Projects № 2 and 24 are financially supportedin part by the Bulgarian National Science Fund of the Ministry of Education and Science. Project № 17 is financially supported by NATO’s Lincage Grant.

INTRODUCTION

This annual report presents the activities of the Central Laboratory of Mineralogy and Crystallography during the 7th year of its existence.

The topics developed were in accordance with the preliminary specified scientific and applied priorities. The most significant scientific results, published or reported at conferences can be grouped as follows:

Studied are the mineralogical composition, the peculiarities, and the processes of formation of various ore deposits and lithological bodies and models are developed for the formation of barite mineralization in the carbonate medium of the Kremikovtsi deposit, the tungsten-iron ochres in Grantcharitsa deposit, and dissipative structures of fluorite aggregates from the Slavyanka deposit. Various bodies of granitoid and volcanic rocks in SW Bulgaria are isotopically dated. An ideological scheme of the entire mathematical spatial representation of arbitrary mineralogical objects is outlined. The chemical and mineralogical composition of the coal and products of their burning for the Pernik coal region are characterized.
The synthesis of 8 phases of microporous and layered titanosilicates suitable for catalysts, ion-exchangers, selective adsorbent, etc., is optimized. For the first time 7 metal and organic hydrogenesquarates are synthesized, with potential non-linear optical properties as well as metal and ammonium salts of the phosphonic acid with possible applications in phyto-pharmaceutical industry. Synthesized and characterized are 4 Synroc composite materials with a simulative addition of cesium and strontium in order to imitate long-time and stable inclusion of high intensive radioactive wastes in them. The effect of atmosphere oxygen during electrolysis of basaltic melts is studied.
The crystal structures of 3 newly synthesized hydrogenesquarates are solved. Studied is the local structure of two types of microporous materials with important application in industry and the process of nucleation and the phase transition from the amorphous to crystalline state is specified. The structural change near to the domain walls in the ferro-elastic lead phosphate is found and their atomic structure is modeled via various nano-sized clusters. It is proved that structural factors improve the micro-hardness and the ware-resistance of sintered boron-carbide ceramics with differing contents of metal borides. The enthalpy of hydration of a number of porous materials is determined, which can serve as heat-exchangers.

Among the most important achievements of practical character are:

The sorption characteristics of low-temperature hydrotalcite metaphases are studied and a new perspective sorbent for heat-pump systems is suggested.
Through original combination of conventional methods 6 useful and/or potentially dangerous products from five types of coal ashes are obtained aiming at their waste-less and ecological utilization applicable also to ashes from Bulgarian TEPS.
Some mineralogical-technological properties of ashes from Republika and Bobov Dol TEPS are investigated aiming at their utilization in ash-cement mixtures and ash-concretes.

The most important results obtained in the framework of the international collaboration of CLMC are:

According to a mutual scientific project with the University of Ghent, Belgium, studied is the adsorption of NO on ZSM-5 and the microporous titanosilicates ETS-4, ETS-10, and STS, un-exchanged or ion-exchanged with copper, cobalt, nickel, and Au and the formation of metal-nitrosil bonds M-NO stable up to 200oC is established. Nanosized gold supports are obtained with high catalytic activity and possible application to environmental preservation.
According to a mutual scientific project with the “L. Maximilian” University in Munich, Germany, deposited are thin films of nano-sized crystals of silicalite-1, CoAPO5, LTA and MEL zeolites with possible applications as micro-calorimetric gas sensors.
During 2001 the research activity, which was partially disturbed due to relocation of CLMC in a new building, was normalized to a significant extent. In the course of this relocation prophylactics and repairing in all laboratories were performed in order to get them in a working stage. This was a process not finished yet, but at present each working place in CLMC is computerized and connected with Internet by optical cable. A security system is assured for both buildings of the Laboratory and the surrounding areas are cultivated. A collection of minerals found in Bulgaria is partially completed and exposed as “The Mineralogical diversity of Bulgaria”. The scientific equipment of the Laboratory was enriched by three apparatuses, namely, inductively-coupled plasma spectrophotometer, laser microanalyser, and a X-ray diffractometer.

The renewed building and laboratories of CLMC in bl. 107 were officially opened at the 7th of June, 2001, by the President of the Bulgarian Academy of Sciences Acad. I. Yuhnovski and by the Mayor of Sofia, Mr. S. Sofiyanski, in the presence of members of the Scientific Council of BAS, official representatives of scientific institutions, and building specialists. On May the 19th and October the 12th days of open doors for visitors were organized, the first being accompanied by a scientific poster session named “Scientific and applied achievements of CLMC”.

The activity of the Laboratory was presented in a proper way in a separate place in the National Museum “Earth and Man” together with a part of samples gifted by CLMC.

Nikola Zidarov
Sofia, January 2001

RESEARCH TOPICS:

I. MINERAL SYSTEMS:

1. Magmatic and metamorphic minerals and mineral associations in Serbo-Macedonian Massif (N.Zidarov, L. Macheva, E. Tarassova, P. Nenova)

The structural, petrological, and mineralogical investigations of magmatic and metamorphic rocks from the Ograzdenian block of Serbo-Macedonian Massif (SMM) (see Ann. Rep. # 1-6 of CLMC) are enlarged with isotopic studies of some geological bodies. The information obtained is important for clarifying their geological position and the age of the protoliths as well as for the thermometamorphic and geodynamic evolution of the massif.

The Rb-Sr isotopic system is investigated in a whole rock samples from granitoids of Skrat pluton and metagranatoids from Belassitza, Ograzden, and Maleshevska mountains. The measurements were performed in the Laboratory of isotope geochemistry of the Institute of Geology, Ural branch of the Russian Academy of Sciences.

Several bodies of porphyritic granitoids (Skrat pluton) located south of Skrat village in the Belassitza Mountain are emplaced in gneisses from the Belassitza Formation of the Ograzdenian Supergroup and display intrusive or tectonic contacts. Up to now, these rocks are refered to the so-called South Bulgarian granites with age assumed as Palaeozoic. Our petrochemical, geochemical, and mineralogical data indicate that the specified rock types, quartzdiorites, granodiorites, and granites, form an evolutionary trend along the boundary of calc- alkaline and high potassium-calc-alkaline series. Granodiorites and granites are of S-type. On the base of preliminary isotopic data these granitoids are dated as Middle Jurassic (167 ± 9.8 Ma) with an initial ⁸⁷Sr/⁸⁶Sr - ratio of 0.71322. In the vicinity of the studied region a close age value of 153 ± 3 Ma_min has been determined by De Wet et al (1989) only for Arnea granite, croping out in SMM in Northern Greece.

Among the metamorphic rocks taking part in the nappe structure of SMM studied are the porphyritic metagranitoids from the most southwestern sections of the Bulgarian part of Belassitza mountain (Lozen metagranites) and porphyritic and equigranular metagranitoids occupying the central and the eastern regions of Maleshevska and Ograzden mountains. Rb/Sr results give an isochron age of T=304 ± 7,7 Ma. Most likely, this value reveals the protolith age. The figurative points of the samples of porphyritic metagranitoids from Maleshevska and Ograzden mountains show some deviation from the isochrone.

Granitoids and metagranitoids with Hercynian age of protoliths have a widespread manifestation in the basement of Rhodope Massif, in the Srednogorie zone, namely in Sashtinska Sredna gora, in SMM (Delchevski and Strumitsa granites in Macedonia), and in Tesalia region in Central Greece. The existing numerous data for Alpine tectonic activity in the studied region allow to propose a significant participation of Hercynian continetal crust fragments in the Alpine tectonic processes.

The initial ⁸⁷Sr/⁸⁶Sr ratio of 0,71756 ± 0,00024 in the analysed whole rock samples from Lozen metagranites and from Ograzdenian equigranular metagranitoids indicates their typical crustal origin. This value corresponds also to their geochemical, mineralogical and petrographical peculiarities, typical of S-type granitoids (the coefficient ASI is from 0.98 to1.45, with an average of 1.22)

The isotopic data allow to correlate the studied rocks with inner continent S-type plutons of the Hercynian Fold Belt in Central Europe, formed via partial melting of metasedimentary source rocks.

The geochronological data pointing at the existence of Middle Jurassic and Upper Carboniferous acid crustal magmatism allow to fix the age of the crustal thickening processes connected with synmetamorphic overthrusting (in SMM) as no younger then Upper Carboniferous - no older then Middle Jurassic.

On the basis of the K-Ar method the dacitic bodies, situated in the Ograzdenian block are dated as Palaeogene (Middle Rupelian - 32.6-30.6 Ma) [26].

The new datа on the chemical composition and the pequliarities of the main rock forming minerals from Gega Melange Body protoliths show that they belong to one co-magmatic series.

2. Accessory zircon in orthogneisses from the Ograzdenian block of Serbo-Macedonian Massif (R. Titorenkova)

The inner structure and the chemical composition of zircon from equigranular metagranites, porphyritic metagranites and melanocratic enclaves from Ograzden and Maleshevska mountains have been studied.

The zircon structures obtained by an electron microscope operating in regime of cathodoluminescence are much more informative than in back scattered electrons. They reveal a complex crystallization and evolution history. Various morphological types of zircon, structures of growth and alteration are established, related to different stages of formation, namely magmatic and metamorphic or connected with the presence of fluids.

Zircon from equigranular metagranites. The crystals are characterized by presence or absence of a resorbed core and a wide oscillatory growth zonality, which indicates magmatic growing in a large melt volume. Sometimes the core is of idiomorphic, most probably metamict crystal, whereas the overgrowth zone is brighter and homogeneous, formed under metamorphic conditions. These zircon crystals manifest faint and irregular cathodoluminescent light emission which is a typical feature for these metagranites, due to their higher content of uranium and radioactive decay damages (Fig. 1a,b).

Fig. 1. SEM-CL images of the zircon inner structure:
(a) from equigranular metagranites with oscillatory magmatic zonality; (b) from equigranular metagranites, where the magmatic zonality is obscured by re-crystallization (the irregular light zones); (c) from porphyritic metagranites where the zones are partially obscured by radioactive decay and defects in the crystal structure; (d) from melanocratic enclaves in equigranular metagranites with rounded core with traces of zonality oblique to the zonality of magmatic overgrowth; (e) from melanocratic enclaves in equigranular metagranites with idiomorphic core of homogeneous zircon, a dark zone and most probably metamorphic overgrowth.

Zircon from porphyritic metagranites. The K-feldspar porphyritic metagranitoids are more strongly affected by processes of migmatization than the equigranular metagranites. Zircon crystals have a continuous magmatic fine, oscillatory growth (Fig. 1c). Non-symmetric zircon crystals grown from two cores with mutual zonal overgrowth are also present. Such crystals can be migmatic, but they can result from magmatic clustering also.

Zircon from melanocratic enclaves in equigranular metagranites. In most cases zircon crystals are rounded with irregular core (Fig. 1d). There are also idiomorphic cores of homogeneous zircon. A dark zone grown upon these cores probably caused by low concentration of activating elements or by lattice defects (Fig. 1e). Some overgrowths indicate growing under metamorphic conditions. It has been accepted that the rounded grains indicate a final growth under metamorphic conditions, while the idiomorphic crystals had already finished their growth in magmatic stage.

Generalized scheme of the succession in the development of zircon crystals is as follow:

Magmatic growth stage characterized by a fine, parallel, oscillatory zonality observed in all rocks type. ® Metamorphic growth stage is present by a relatively homogeneous growth zone with different width. ® Reorganization processes stage of the crystal lattice affecting the zonal magmatic crystals induced by large differences in U, Th concentration in the adjacent growth zones. It is a solid-state reaction not affecting the external form of the crystals, caused by the radioactive decay. In this case the primary structures are gradually erased and the intensity of the cathodoluminescence emission is increased. The migration of Pb, Th, and U in the crystal leads to homogenization (Fig. 1 a, c, d) ® The recrystallization of zircon crystals is easily distinguished by the irregular light CL zones marking the migration of the chemical reaction front away from the crystal surface towards the core. This process is most pronounced in zircons from equigranular metagranites (Fig. 1b) probably due to their higher degree of metamictization. This is a heterochemical process of substitution leading to a decrease Pb, Zr, and Si content in the altered regions. It is possible fluids on a later, retrograde stage to be responsible for this process, which, according to literature data, leads to rejuvenation of U-Pb isotopic system.

3. Accessory allanites (Ce) from deformed porphyritic granatoids from the Ograzdenian block of the Serbo-Macedonian Massif (E. Tarassova)

In deformed porphyritic granitoids near to Skrit village in Belassitza Mountain often accessory allanites are observed, which, together with biotite, apatite, titanite, and quartz, participate in forming the foliation of rocks (aggregates of these minerals overcoat the microcline phenocrystals). This study presents preliminary data from the investigation of allanite, the main attention being paid to the chemical composition, the phase heterogeneity and the alteration of the mineral.

Allanite forms prysmatically elongated crystals, sized up to 3 mm. Main feature of all the crystals studied is the presence of: (1) fissures and tracks of alpha-particles indicating metamictic alterations of the mineral; (2) a great amount of inclusions of apatite crystals, frequently oriented with respect to the embedding matrix; (3) the same type of transformations resulting in successive topotaxial replacement of the primary allanite I with allanite II and epidote.

For all the parts of allanite I studied close contents of rare earth (Ce,La, Nd, and Y) and radioactive elements (U and Th) were observed. The maximum contents of these elements found are as follows (in wt.%): 11.5 for Ce₂O₃, 5.4 for La₂O₃, 4.7 for Nd₂O₃, 3.0 for ThO₂, 1.3 for UO₂, and 0.44 of Y₂O₃. Characteristic of the studied allanites is a ratio Ce/La close to 2:1.

Allanite II develops both in volume and along the periphery of the crystals of allanite I. The formation of allanite II in the volume of the primary crystals is related with the presence of system of tracks and fissures, which are suitable channels of the transport of chemical components. In this case allanite II forms either randomly shaped grains or reaction zones around fissures. Epidote replaces allanite II predominantly along the periphery of the primary allanite crystals. The initial morphology of the allanite I crystals is totally preserved during its transformation into allanite II and epidote. The topotaxial transformation of allanite I (allanite I - to allanite II - to epidote) proceeds during the sequential alteration of the mineral chemical composition, i.e. a decrease in the content of REE, U, Th, and Fe²⁺ and an increase in the content of Si, Al, Ca, and Fe³⁺.

4. Spectroscopic study of fluorite from Bulgarian ore deposits (B. Zidarova)

The complex use of spectroscopic methods in studying fluorite from Bulgarian industrial deposits (see Ann. Rep. 6 of CLMC) allowed to find important knowledge for the conditions of fluorite formation. The analysis of these spectral results makes it possible to evaluate the conditions of formation of crystals and aggregates as they are conducted on local, structurally manifested and differently colored zones in the crystals. New information is obtained for the evolution of the hydrothermal system.

The temperature and pH of the hydrothermal solutions forming the fluorite in these deposits (on the basis of data for gas-liquid inclusions) is as follows: for Slavyanka T^o = 93-210^oC and pH@6; for Mikhalkovo T^o = 110-190^oC and pH=4.95-5.52; for Chiprovci T^o = 150-300^oC.

The transport of fluorite in these solutions realizes through fluorine (F^-), silicofluorine (SiF₆^2-), alumofluorine (AlF_n^3-n), and other complex ions.

The stability of these complexes depends mainly on pH of the medium, namely on whether pH <6 or pH > 6. One can not exclude the possibility for the presence in the hydrothermal solution of the so-called "aqueous complexes", which are responsible for the form of migration of silicon (Si⁴⁺), the alkaline elements R⁺ (Na⁺, K⁺), and R³⁺ (Al³⁺, Fe³⁺, TR³⁺, etc.), which, upon destruction result in the formation of quartz, clay minerals, and TR in fluorite in the deposit (Fig.1).

The physicochemical parameters of the mineral-forming medium (pH, Eh, etc.) are specified for fluorite from the deposits Slavyanka, Mikhalkovo and Chiprovci, and the effect of T^o_formation on the form of inclusion of TR therein is established.

Data on the own defects and TR³⁺ in fluorites are obtained using X-ray luminescence. The parameters revealing the variations in the content of the most characteristic defects and their combinations are: A=IDy³⁺_cub.(572)/IF^-₂₍₂₉₆₎, reflecting the concentration ratio for activation centers and centers of own defects in the fluorite structure; B=IDy³⁺-O^2-₍₇₅₄₎ /IDy³⁺_cub.(572), reflecting the degree of inclusion of oxygen ions in the fluorite structure; C=SI_TRY/SI_TRCe, presenting the ratio of the integral intensity of lines corresponding to centers of ions of Y and Ce subgroup; D=ISm³⁺-O^2-₍₆₀₅₎ /ISm³⁺_cub.(567) has the same meaning as the parameter B; E=IEr³⁺-Na⁺₍₅₄₀₎ /IEr³⁺-O^2-₍₅₃₃₎ is a measure of the degree of inclusion of Na⁺ and O^2- ions in the fluorite structure. These parameters are illustrated in Fig. 2 for the three deposits.

Using thermo-luminescence data are obtained for the content of TR²⁺. Most intense are the maximums on the curves corresponding to the primarily deposited highest-temperature fluorites in the three investigated deposits. These are: the defect center (YO₂)^o (at 180^oC) - Slavyanka, Mikhalkovo, Chiprovci; center Y²⁺-TR⁴⁺ (at 240-270^oC) - Chiprovci; cubic center Y²⁺ (at 280^oC) - Slavyanka, Mikhalkovo, Chiprovci; center (TRO₂)^o (at 320^oC) - Slavyanka, Mikhalkovo; center Dy²⁺-Ce⁴⁺ (at 350^oC) - Mikhalkovo; center Sm²⁺-Ce⁴⁺ (at 380^oC) - Slavyanka, Mikhalkovo. The large abundance of TR²⁺ indicates a sufficiently low oxidation-reduction potential of the solutions, from which the early, high-temperature fluorites in the deposit of Slavyanka (type I and II^a) had crystallized. For the fluorite type II^b and II^c from Slavyanka and Chiprovci deposit characteristic are higher values of the oxidation-reduction potential and lower temperatures (most probably with charge compensation of the type O^2-® F^-) as well as a very low content or even absence of TR²⁺. The higher temperature fluorites are characterized by peaks in the thermo-luminescence curves at higher temperatures than those for the lower temperature types. The presence of capture levels at T^o=350^oC is characteristic of fluorites formed through metasomatic replacement under conditions of an increased oxidation-reduction potential in the medium (Mikhalkovo deposit). Fluorites with octahedral habit are formed under more pronounced oxidation conditions [(TRO₂)^o prevails] than those with cubic habit in the Mikhalkovo deposit. It is noticeable that for fluorite with octahedral habit and for the granular-secretional fluorite from the same deposit characteristic are centers of hole capturing while for the metasomatic fluorite and that with cubic habit - centers of electron capturing.

Using optical spectra of transmission and absorption it was found that in the course of progression of the fluorite formation the content of TR decreases, which makes it possible to use some of the fluorites in these deposits as raw material for growing single crystals of optical grade or directly to prepare elements for optics.

5. Mathematical model for the growth of fluorite aggregates in caverns in Slavyanka deposit (B. Zidarova, M. Marinov, N. Zidarov).

A mathematical model is proposed for the formation of fluorite aggregates in Slavyanka deposit, which describes the origin of dissipative structures resulting from self-organization of the mineral-forming medium.

In the vein-type fluorite deposit Slavyanka, SW Bulgaria, fluorite aggregates of a specific structure cover the walls of the great caverns formed due to motions in the plane of the strike-slip fluorite-bearing fault. They belong to the mineralogical variety II, deposited during the III impulse of hydrothermal activity.

In geologic processes a great part of the stationary systems originates and exists in a fluid flow being in equilibrium under stationary conditions. In opening the caverns the motion may be realized as a laminar flow determined by the dimensionless Reynolds number Re = oul/m, where o is flow mean rate in the solution, l is the characteristic size of the convective structure, and m is the solution viscosity. When the critical velocity is approached, the laminar flow becomes turbulent, e.g. via period doubling. With increasing Rayleigh number a very complicated motion occurs and when it reaches the serial critical value the period doubles. Such is the case of formation of the fluorite variety II. The model considered is valid only when there are no exothermal reactions acting in the fluid influence zone (the fluorite formation is accompanied by endothermal reaction).

The great deviation of the system from equilibrium requires the use of non-linear equations as a mathematical tool. These equations account for the possibility for the existence of several stationary states, the most probable being that which is stable to fluctuations and has minimum free energy.

The dependence of the solution concentration on the distance to the boundary surface for differing values of a in the range from 0.1 to 100 is illustrated in Fig. 1. It has been found that for large values of a (fig.1) the concentration changes substantially only at small distances (boundary layer) away from the boundary surface.

The measurement of the samples in a given cavern (see table 1 and fig. 2) shows that the transversal cell size (in the greatest cross-section) is l » 0.5 cm.

Fig. 1

Table 1. Basic data of the mathematical model

Fig. 2. Geological sketch plan of the part of a Main fluorite vein with cavernes, level 80, Slavyanka deposit in scale 1:500.

One obtains a » h/0.5 andfor h » 25 cm (the mean distance from the cavern center to the growing surface), a » 40.

Finally, replacing for a, one obtains w »r(0)Dc₀/(lr_F).

The quantities in this equation have the following values r_F» 3180 kg/m³; r(0) » 1000 kg/m³ ; l» 0.6 cm; D » 10^-6 cm²/s; c₀» 1% and thus, gives w» 5x10^-9 cm² /s.

If one takes into account that in convection the velocity is about twice greater, w » 10^-8 cm²/s.

Accounting for the approximations in the model, the obtained value for the growth rate of fluorite is comparable to that measured in laboratory experiments. The same correspondence has been observed for the growing time of quartz crystals in nature and in laboratory autoclaves.

The model proposed for the formation of fluorite aggregates from Slavyanka deposit is an alternative possibility to the mineralogical concepts for the growth of mineral aggregates, which relates their structure with the dynamics of the forming medium [64].

6. Genetic model of the barite ore formation in the Kremikovtsi deposit, Bulgaria (Z. Damyanov)

The composition of fluid inclusions in representative samples from various mineralogical-genetic types of endogenic and supergenic barite from the Kremikovtsi carbonate-hosted sedimentary exhalative iron(+Mn)-barite-sulfide deposit, Western Balkan, Bulgaria, was studied. The data obtained show that the major components in the fluids are represented by Cl^-, SO₄^2-, Na⁺ and K⁺. The solutions forming the endogenic barite may have relatively low contents of SO₄^2-, Na⁺ > K⁺ and dominant chloride composition. It was established a decrease of the Na⁺, Cl^- and Br^- concentrations from earlier toward later barite mineralogical types at the expense of the relative increase of K⁺. As a rule, the higher amounts (40-20) of the Na/K molar ratio and Cl^- concentrations decrease with the incrfeasing of the temperature of homogenization of the gas-liquid inclusions and the K/Br ratio. The Cl/Br and Na/Br ratios are lower than in the seawater, thus indicating a mixed origin of the barite-forming solutions most probably from ascending heated formation waters passing through enriched in organic matter sediments and mixed with descending cold (probably marine) waters in the process of hydrothermal convection at the zone of embrional rifting, which is the reason of their mobilization and moving up.

A geological-genetic model of the epigenetic veinlet-disseminated phyllosilicate-sulfide-barite mineralization in the primary iron carbonate ores and host rocks from the Kremikovtsi deposit was created (Fig. 1) [4]. Epigenetic hydrothermal activity attacked the iron carbonate sediment most probably at the stage of burial diagenesis and advanced lithification. The invasion of hot (200^o-230^oC), strongly aggressive, acid (pH = 3-5) hydrothermal solution into a carbonate medium provoked intensive dissolution controlled by the initial microtectonic framework. A generalized sequence of mineral formation is established in such a setting, as follows: (1) prismatic quartz - I-S, (2) chamosite rosettes - barite, (3) barite - sulfides - bladed chamosite, (4) kaolinite - berthierine - barite. The common trend is controlled by the gradual alkalinity of solution at a slightly varied P_O2 near the boundary of sulfide/sulfate stability. The textural relationships of the mineralization studied show no indications of repeated invasion of hydrothermal solutions in the host setting. They give a reason to propose a metastable equilibrium realized between sulfides, phyllosilicates and sulfates (barite) at the temperature of mineral formation (200-230^oC) and their common, but without any signs for mutual corrosion, association at relatively stable reducing conditions (log P_O2slightly lower than -30, i.e. near the sulfide/sulfate stability boundary) (Fig. 1c and d).

Fig. 1. Generalized sketch of proposed phyllosilicate mineral formation in the Kremikovtsi SIF: a) Schematic sequence of ore formation based on the petrographic features observed. The whole petrographic variety of carbonate diagenesis (e.g. insignificant intraclastic resedimentation, microsparitization of initial micrite, etc.) and hydrothermal deposition in open spaces is not included (not to scale); b) Stability relations among siderite-berthierine-FeS-Fe(OH)₃ as a function of P_CO2 and P_O2 at pH = 8, S = 10^-6(the hypothetical generalized trends of the proposed development of mineral formation are presented by arrows); c) Phase equilibrium and stability fields of the hydrothermal mineral formation at 200-300^oC, [K⁺] = 0.1 mol/l, and [еS] = 0.01 mol/l as a function of pH and P_O2. The hatched area limits the field of ferrous chlorites. Chl²⁺ - ferrous chlorite; Chl³⁺ - ferric chlorite; Hem - hematite; KFs - K feldspar; Mt - magnetite; Mu - muscovite; Py - pyrite; Pyr - pyrrhotite; Pyp - pyrophillite; Q - quartz; d) logP_O2 as a function of temperature of hydrothermal barite formation.

The model described or some of its elements may be useful at the genetic interpretations of other epigenetic barite-sulfide deposits in carbonate rocks. On the other hand, the established basic characteristics of the associated phyllosilicate mineralization can be used to distinguish syn- and epigenetic ore bodies in stratiform polymetallic deposit of SEDEX-type as a suitable criterion for evaluation or revaluation of their ore potential [4].

7. Genetically indicative features of Pt-Fe and Os-Ir-Ru alloy crystals from placers in SW Bulgaria (Z. Tsintsov)

Pt-Fe and Os-Ru alloy crystals from the sediments of Kyustendil and Gotse Delchev grabens, SW Bulgaria, were investigated [41]. Pt-Fe alloy crystals are presented by cube and octahedral simple forms and combinations of {100} and {111} faces sometimes with {110} face. The crystals of Os-Ru-Ir alloys include osmium and rhutenium minerals and are presented by combinations of hexagonal prism, hexagonal bipyramide, and basic pinacoid. The primary morphological features of the crystals, the relatively monotonous and constant composition and the character of the inclusions (Pt-Fe alloys, osmium, cuprorhodsite, bowieite, bornite, Cr-spinel, and clinopyroxene) show that they are of magmatic, high temperature origin, Pt-Fe alloys having been firstly formed. Their secondary morphological features are connected only with the mechanical transport in the placer. Dunites and peridotites from the bounding massifs of the grabens are the most perspective sources of the crystals investigated.

8. Mineralogy and conditions of formation of ore associations in ultrabasites and listwenites (Z. Tsintsov)

The noble metal mineralization, including native gold, native silver, accantite, and Pt-Fe alloy in listwenites from the region of Svetulka village, Kurdjali district (Central Rhodopes) is investigated. Listwenites are of predominant carbonate composition and crop out in the eastern part of the massif. During the last 25-30 years the associated placers have been intensively processed (manually by private persons) for mining native gold. In some areas its content reaches up to n.10 g/m³. Our studies on this kind of gold show that its grains are predominantly sized mainly above 200 mm up to 1.5 cm, isometric and relatively weakly deformed in the placer. A number of geologists have accepted listwenites as a primary source of this gold. The relatively sporadic knowledge on them up to now does not indicate the presence of native gold. The chemical analysis data of the listwenites considered (including a sample with Au-Ag-Pt mineralization) show a very low content of Au and Ag (below 0.03 ppm and below 1ppm, respectively). The investigation of more than 20 polished sections prepared from samples all along the profile of the listwenites (from areas of a predominantly quartz composition to such of a predominantly carbonate composition) revealed the presence of spinels (iron or chromium containing) in the majority of the samples studied. Only for one of the samples the specified mineralization was observed established in listwenites with a predominanly carbonate composition, which, after re-calculation of the chemical analysis data show a calcite content of about 78%. The remaining minerals forming the rock (on the basis of optical microscopy data) are quartz, potassium feldspar, biotite, and accessory appatite. The dominant part of them is confirmed also by powder X-ray diffraction analysis (calcite, quartz, Ca-feldspar).

9. Crystal chemical peculiarities of minerals from metasomatic zones (Y. Tzvetanova)

The crystallization succession and the crystal chemical formulae of minerals from zoned calcic skarns embeded in monzonites from Zvezdel pluton are investigated. Skarns consist of pyroxene - garnet and garnet lenses, surrounded by the following concentric zones toward the intrusive contact, namely plagioclase - pyroxene-wollastonite - garnet ± scapolite, plagioclase - pyroxene - wollastonite - epidote, and plagioclase - pyroxene.

The microprobe analysis confirmed three types of garnets: melanites with TiO₂ content of 8 to 11 wt. % and andradite component from 63 to 84 wt. %; grossularite-andradites with andradite from 46 to 54 wt. %; and garnets of a high content of grossularite - 70-80 wt. %. Among all established garnets melanites are found to be formed earliest and only in the garnet and garnet-pyroxene zones. The concentration of Fe³⁺ lowers during the succession of the bimetasomatic process and the garnets with a grossularite component of 70-80 wt. % formed at the end. On the bases of microprobe data it was confirmed that two types of pyroxenes are present,namely subsilicic aluminian ferrian diopside (known as fassaite) and diopside-hedenbergite. Fassaite is observed only in the garnet-pyroxene zones usually included in garnet grains, whereas diopside-hedenbergite is present in all other zones. The component ratios in the case of the fasaite type pyroxene is S₃(Al)_8-15 Es_17-21S₄(Mg)_8-9Hd_5-42Di_25-59. The hedenbergite component in the diopside-hedenbergite type of pyroxene varies from 43 to 75 wt. %. The other primary skarn minerals are wollastonite, epidote with a pistacite component of 16 to 31 wt. %, plagioclase (An_55-36), scapolite (with about 80 wt. % meionite component), titanite, apatite and magnetite.

The mineral assemblage in the skarns can be interpreted as phase relations in the simple system, CaO-Al₂O₃-Fe₂O₃-SiO₂. According to the reaction fassait + wollastonite ® andradite one can proposed a maximum temperature of about 935° C at 1 atm in the xenolith. On decreasing temperature andradite remains as a stable phase coexisting with fassaite and wollastonite. With a further decrease in temperature below 798° C the garnet transformed to the more stable grossularite-andradite type. The further decrease in temperature at constant pressure and bulk composition the content of grossularite in grandites increases. The formation of skarn epidote at a temperature of about 400-500° C and at 1 atm can be accepted as a lower temperature limit for the skarn formation [60].

10. Mineralogical map of the heavy mineral concentrates in Bulgaria (O.Vitov)

The archive of the mineralogical composition and the coordinates of the sampling of the heavy mineral concentrates is completed on the basis of maps disposed in the National Geological Database. Data on coordinates and mineralogical composition are completed for 132 406 samples (formal and logical control). Presented is the distribution of the data concerned with authors, the statistic characteristics of minerals in the heavy mineral concentrates and analysis of the scale density of sampling [48]. It is found that the Bulgarian territory is sampled using a random set of mapping, which provides only a general view for the distribution of minerals and mineral associations (Fig. 1). A serious potential is also established for prospecting tungsten ores, gold, barite, non-ferrous metals, kyanite, bismuth, tin, mercury, and other mineral ores. It is recommended that actualization of the heavy mineral concentrates mapping and enlargement of the data base with new data is necessary.

Fig. 1. Completeness of the heavy mineral concentrates mapping in Bulgaria.

A prognosis is performed for the heavy mineral concentrates aiming at prospecting of gold mineralization in Bulgaria (see Fig. 2) [49]. It is found that on the territory of Bulgaria gold results from thermal gradient re-distribution and enrichment in stripes differently oriented during the different geologic epochs. The stripes directed at 45°and 165°, probably youngest in age, are dominant and in their links (Eastern Rhodopes Mt., Kraishte, Western Sredna Gora Mt., Western Balkan Mt., and the Kazanluk region) the greatest accumulation of gold is registered.

Fig. 2. Prognosis map for prospecting gold mineralization in heavy mineral concentrates.

A prognosis estimate is carried out for prospecting tin mineralization in Bulgaria. The regions of accumulation of samples containing cassiterite and minerals, which are correlates of cassiterite are described [63]. Revision samplings in the perspective areas are proposed to be performed (Fig. 3).

Fig. 3. Prognosis map for prospecting tin mineralization in heavy mineral concentrates.

II. ENVIROMENTAL MINERALOGY

11. Mineralogy and geochemistry of coals and coal products (S. Vassilev, Chr. Vassileva)

A combination of conventional methods including sink-float, magnetic, sieving and froth flotation separations, as well as leaching, vaporization and crystallization procedures were used to recover 6 useful and/or hazardous products from coal fly ashes of Spanish thermo-electric power stations for a multicomponent, wasteless and environmentally friendly utilization of these fly ashes. Various physical and chemical analyses have been conducted to characterize the phase-mineral and chemical composition of the products derived [45]. The behaviour of mineral matter in 6 Bulgarian coals (Sofia, Maritza West, Maritza East, Bobov Dol, Balkan, Pernik) during their gradual heating in air was studied. Some correlation trends between the mineral and chemical composition of these coals and their ash-fusion temperatures were found (Fig. 1). The geochemistry of chlorine and bromine in various Bulgarian coals was studied and some general observations on the migration, concentration and distribution of both elements were discussed [55].

The present state of the commonly used methods for inorganic and mineral matter characterization in coal was described and summarized. A critical overview on the advantages and disadvantages of the methods during their application was also performed. The chemical composition, including major (Al, Ca, Fe, K, Mg, S, Si, Ti), minor (Na, P) and trace (Br, Cl, Co, Cr, Cu, Li, Mn, Ni, Pb, Rb, Sr, Zn) elements and mineral matter of the Pernik subbituminous coals and their preparation and combustion solid waste products were studied. Feed coals, upgraded coals (high-grade and low-grade coals) and their waste products, namely coal slimes and host rocks generated from the Pernik coal preparation plant, as well as combustion waste products such as bottom ashes, fly ashes and lagooned ashes resulted from the "Republica" coal-fired thermoelectric power station were characterized. The occurrence and behaviour (partitioning, volatilization, condensation, capture and retention) of the above-mentioned elements and various minerals during coal preparation and combustion are described.

Fig. 1. Correlation trends between detrital-authigenic index (I) and ash-fusion temperatures (AFT) for high-temperature (815^oC) ashes of some Bulgarian coals.

12. Synthesis of artificial rocks (SYNROC) (I. Donchev, Fr. Dipchikov, O. Petrov, M. Tarasssov, N. Zidarov, L. Petrov)

A new series of experiments was performed in order to prepare original compositions of SYNROC materials. As starting shichts used were oxide precursors of Al₂O₃, BaCO₃, TiO₂, ZrO₂, Cs₂O, and SrCO₃ in quantities, re-calculated for directed crystallization. Four products were obtained from the designed starting compositions, namely: 1) with addititon of 3 % Cs₂O and 2% SrCO₃; 2) with addition of waste Ni catalyst; 3) with 1% metallic Ti; and 4. with addition of a by-product of ferro-vanadium slag and white barite concentrate instead of CaO, Al₂O₃, and BaCO₃.

The solid-state synthesis was performed in a "Supercantal" furnace. The mixtures were firstly well homogenized with isobutyl alcohol, then pressed to form tablets, placed in corundum vessel and covered with corundum powder. From the bottom to the top the composition arrangement followed was from 1, through 2, 3, up to 4. The samples were heated in the range 20 to 1320^oC for a total of 11 hours with a time delay of 2 hours performed in the range 1300-1320^oC.

The sample bodies of Synroc are characterized with irregularly grained holo-crystalline structure, which is not completely dense and on places display caverns and varying in shape voids.

The Synroc materials obtained were studied with XRD, SEM, and EDAX microprobe analysis. It was established that in the samples formed are perovskite, hollandite-like phase, zirconolite, and rutile and in sample 4 in addition formed are corundum and calcium hexaaluminate, namely ibonite (Figs. 1 and 2). Similarly to the first four minerals the latter two can be related to the group of the so-called host lattice structure type.

Fig. 1. Powder X-ray diffraction patterns (XRD) of Synroc compositions 1 and 4 (CoKa, 18-62o 2q). Legend: H is hibonite, hol is hollandite, P is perovskite, Zr is zirconolite, R is rutile, and C is corundum.

The microprobe analyses performed allow, to clarify on this stage that hollandite is of non-stoichometric composition and strongly disordered structure. The derived crystal chemical formula for hollandite, (Ca_0.08Ba_0.04Zr_0.08 )_0.2[Ti_5.01Al_0.33]_5.34O₁₆, characterizes this phase as hollandite-like one with possible inclusion of other ions. The formula (Ca_0.81Sr_0.1)_0.91[Ti_1.02Zr_0.02]_1.04O₃ was calculated for perovskite.

Fig.2. Microphotographs of Synroc samples (SEM Philips 515). a - #3 - X 2500, b - #4 - X 10 000, c - #3 - X 2400, d - #3 - X 2500, hol – hollandite, h – hibonite, C – corundum, P – perovskite, Zr – zirconolite.

13. Mineral and technological properties of fly-ashes from thermoelectric power stations "Republika" and "Bobovdol", Bulgaria (I. Donchev, A. Lenchev, J. Ninov, L. Gigova)

Properties of fly ashes coal fired in TEPS "Republika" and "Bobovdol", were investigated. The study was carried out to establish the possibilities for production of fly ash cement. The results on the chemical and mineral composition, the pozzolanic activitie, and the physical properties show that both types of fly ashes are appropriate for this purpose.

The mineral composition of the fly ashes was determined using optical, XRD, SEM and microprobe chemical analyses [7]. The contents of the active SiO₂ and Al₂O₃ estimated on the basis of the total chemical, mineral and microprobe analyses corresponds to the standard requirements for the content of these oxides in fly ashes aiming at production of fly ash cements.

The activity of the initial and the grinded fly ashes was found to be high and fly ashes are characterized as being highly active artificial pozzolanas (determined as the amount of CaO added to 1 g fly ash in accordance with standard method requirements, BDS 16720, 1987). For the coarser material from TEPS "Bobovdol" the increase in the fineness is accompanied with a considerable increase in the reaction rate. For the initial and the grinded fly ashes from TPS "Republika" the rate of the reaction is high and the difference between them remains relatively small (Fig. 1).

Fly ash-cement mixtures were prepared and their physical-mechanical properties were determined. For the cement mixtures containing 30 % fly ashes, the strength after 28-day storage of the samples under standard conditions corresponds to cement type PC 32.5.

Fig.1. Kinetic curves of the pozzolanic activity versus time: 1, 1'- starting and grinded fly ashes from TPS “Bobovdol”; 2, 2' - starting and grinded fly ashes from TPS “Republika”

14. The effect of natural sorbents (Egyptian bentonite-Bulgarian clinoptilolite) as filters in purifying polluted waters (B. Vassileva, O. Petrov, S. Hammad)

The possibilities for removing ion pollutants from water using filters of natural layered (montmorillonite) and framework (clinoptilolite) alumosilicates are discussed. For the case a comparative study is performed of the sorption effectiveness of materials from Bulgarian and Egyptian bentonites combined with clinoptilolite tuff from Eastern Rhodopes, Bulgaria. Water solutions corresponding to waste water of a high content of ion-pollutants were obtained using CuSO₄.5H₂O, CaCl₂, ZnSO₄.7H₂O, and KNO₃. A sorbent sample from Bulgarian clinoptilolite and bentonite mixed in a ratio 3:1 is used as reference (R) and two other mixtures prepared from clinoptilolite and bentonite from Egypt mixed in ration 3:1 and 2:1 are studied to evaluate the cleaning effect on the model waste water. This effect is illustrated in the figure where the content of the polluting cations is plotted against the volume of the model water passing through the sorbent, "cpt" stands for clinoptilolite and "mnt" for bentonite.

The obtained results show that the used combinations of the natural sorbents can be effectively applied to cleaning different types of polluted waters. The Egyptian bentonite displays slightly lower purification ability than that of the Bulgarian bentonite, but may be used successfully for cleaning of waste waters of lower concentration of ion polluants [46].

15. Adsorption of NO on supported transition metals (Yu. Kalvachev)

To clarify the DeNO_x processes on supported transition metals, the adsorption of NO on ZSM-5 zeolite and on microporous titanosilcates ETS-4, ETS-10, STS, either unexchanged or exchanged with Cu, Co, Ni, and Au, are studied. The main technique used is in-situ infrared spectroscopy (IR), which is a powerful means for monitoring adsorbed species on catalyst surfaces.

After adsorption of NO on surfaces of Cu-ZSM-5, Co-ZSM-5, and Ni-ZSM-5, prepared by ion-exchange, new absorption bands in the spectral range 1960-1840 cm^-1were observed in the IR spectra. They are assigned to metal-nitrosyl species M-NO. For Cu-ZSM-5 bands appeared at 1907 and 1830 cm^-1. The former is assigned to Cu²⁺- MO nitrosyls and the latter to Cu⁺- NO, revealing an easy reduction of Cu²⁺ to Cu⁺. No linear Co²⁺- NO species was observed during the NO adsorption on Co-ZSM-5. At the same time spectral bands at 1901 and 1820 cm^-1 were detected, attributed to dinitrosyls, which are stable and observable even upon evacuation at 200^oC. After NO adsorption a spectral band at 1876 cm^-1 combined with a small shoulder at 1885 cm^-1 was observed in the spectrum of Ni-ZSM-5. The frequency of Ni²⁺ - NO species is usually detected near to that of gaseous NO. The shoulder disappeared upon heating.

In order to obtain nanosized gold samples of high catalytic activity gold was deposited on ZSM-5 and on ETS-4 and ETS-10 microporous titanosilicates using the deposition-precipitation method.

Adsorption of NO was also performed using metal-unloaded titanosilicate molecular sieves. For ETS-4 two bands at 1406 and 1363 cm^-1 were observed still existing after evacuation at 250^oC. These bands are assigned to adsorbed species of nitrogen in a higher oxidation state, 3 or 5, typical of nitrito, -O-N-O^- and nitro NO₂ - anions.

III. MODELING AND MODIFICATION OF MINERAL SYSTEMS

16. Geometrization of the language of mineralogy (V. Penev, N. Zidarov, B. Zidarova)

Based on the categories structure, composition, and construction already defined [59], the basic notions free chemical point, bonded chemical point and chemical graph representing the geometrical images in the space of chemical structures V_s(6) corresponding respectively to free (unbonded) simple chemical objects, bounded simple chemical objects, and complex chemical objects and the logical analysis performed it can be concluded:

I. A method for entire mathematical spatial representation of basic mineralogical and crystallographic notions is developed.

II. Using this method logically and correctly defined are such basic mineralogical, crystal chemical, and crystallographic notions as entirely ordered chemical structure (e.g. crystal lattice, a body with a long-range order), partially ordered chemical structure (e.g. a fluid, a body with short-range order), totally disordered chemical structure (e.g. gases, amorphous solids), elementary cell, mineral, etc.

It is shown that:

At any moment: a) every simple chemical object can be represented entirely mathematically through defining the coordinates of the corresponding chemical point in the space of chemical structures V_S(6) (the definition of V_S(6) is given in Annual Report 3/1997 of CLMC); b) every complex chemical object (including every mineralogical object) can be represented entirely mathematically through defining the corresponding chemical graph in V_S(6).
The notions free chemical point, bonded chemical point, and chemical graph cover the all variety of chemical (including mineralogical) objects and are sufficient for the entire mathematical representation of their arbitrary combinations, both totally order and partially and totally disordered.
The structure of every complex chemical (including mineralogical) object is represented entirely mathematically through defining in V_S(6) of the corresponding chemical graph, representing the given complex object.
The composition of every chemical (incl. mineralogical) object is represented entirely mathematically through defining in V_S(6) of the set of the apexes of the corresponding chemical graph representing the given complex object, i.e. through defining the corresponding set of bonded chemical points.

The construction of every complex chemical and mineralogical object is entirely represented mathematically through defining in V_S(6) of the set of edges of the corresponding chemical graph, representing the given chemical object.

The role of figures in the space of chemical structures V_S(6) is played by the chemical points and chemical graphs, while that of transformations in this space is played by the well known geometrical transformations of the ordinary physical space V_E(3) and motions , and in the Mendeleev's space V_M(6).

Every entirely ordered chemical structure (i.e. both composition and construction of every crystal lattice) is represented entirely mathematically and uniquely in V_S(6) through the corresponding periodic chemical graph.

For each periodic chemical graph (i.e. for each crystal lattice) there exists such a minimum chemical graph (named elementary graph or elementary cell), through which by translations along the three directions in the ordinary three-dimensional physical space V_E(6) one obtains the given periodic chemical graph representing the corresponding entirely ordered chemical structure.

The set of chemical structures includes the subsets of the objects with natural and such with synthetic origin. In the language of mineralogy the entirely ordered natural objects of earth inorganic origin and with definite composition is referred to as minerals. That is why every periodic chemical graph, representing mineral will be referred hereafter to as mineral graph. It is clear from the foresaid that mineralogy is a science for the mineral graphs in the space V_S(6) and for their possible transformations.

17. Regularities in synthesizing titanosilicate phases (V. Kostov-Kytin, S. Ferdov, F. Verpoort, Yu. Kalvachev, O. Petrov)

Eight pure crystalline titanosilicate phases were synthesized without using organic compounds as chemical sources or templates in the course of low-temperature hydrothermal syntheses in the system Na₂O-K₂O-TiO₂-SiO₂-H₂O. These are the microporous ETS-10, ETS-4, STS and GTS-1, layered AM-4 and JDF-L1, and two dense titanosilicate phases analogous to the minerals natisite and paranatisite. For the first time, nano-sized Na-GTS-1 was synthesized. The identification and characterization of the phases were carried out by powder X-ray diffraction, Raman and IR spectroscopy, SEM, BET-surface analysis, TG and DTA.

In the course of studying the role of various physicochemical parameters during the synthesis of titanosilicates it appeared that the content and the ratios between Na₂O, K₂O and TiO₂ in the initial batches influence most the type of the synthesized phases, as well as the size, orientation and morphology of the run-products and their symmetry [57]. That is why, most detailed investigations were performed in the system aNa₂O-bK₂O-cTiO₂-10SiO₂-dH₂O, where 0ЈaЈ9, 0ЈbЈ9, a+b=9, 0.4ЈcЈ3.3, 675ЈdЈ1100 and in the system aNa₂O-bTiO₂-10SiO₂ -675H₂O, where 3ЈaЈ30, 1ЈbЈ4, at synthesis temperature 200°C, crystallization time 24 h and autogenous pressure.

Kinetic investigations carried out in the above systems gave evidence of successive phase transformations leading to the appearance of more thermodynamically stable products. The successive replacement of synthetic paranatisite by natisite is a good example of the validity of Ostwald's rule of successive transformations among the members of the group of titanosilicate compounds, with potential for interesting industrial application [58].

A part of these investigations was realized with the University of Ghent, Belgium, with financial support from the project under reference SA (EST.CLG 977518)5941 approved by the Advisory Panel on Environmental and Earth Science & Technology of the Scientific and Environmental Affairs Division, NATO, Brussels.

18. Evaluation of low-temperature hydrotalcite metaphases as heat exchangers (N. Petrova, T. Mizota, Ts. Stanimirova)

In order to search for suitable heat exchangers at various dehydration temperatures, hydration enthalpy of many hydrous materials were investigated such as natural, Na-, K-, Ca-, Mg-exchanged clinoptilolite [32] and H-type zeolites [72].

Assuming H₂O as an independent component in the zeolite structure it was experimentally proved that zeolitic water is in a very low entropy state (3 Jmol^-1K^-1). This fact provides the background for operation of a zeolite-water heat-pump system, suitable for relatively low temperature heat sources such as solar heat and waste heats from factories [25].

Enthalpies of hydration of low-temperature hydrotalcite metaphases (HT-D and HT-B) were measured by means of the adiabatic water-vapor absorption calorimeter aiming to evaluate a new prospective heat exchanger material [31,70]. The metaphases are characterized by Mg/Al ratio of 3:1 and CO₃² - interlayer group. HT-D results in partial or full dehydration of HT (up to 100-160^oC) without any changes in the lattice parameters. The partial dehydroxylation of brucite-like layer up to 230^oC reduces the interlayer spacing and changes the carbonate group symmetry, thus transforming the structure into that of HT-B. The sorption volume of rehydrated HT-B becomes larger by about 50% that of HT due to both the expansion of the interlayer thickness and grafting of the CO₃² - group into the brucite layer. These structural peculiarities of HT-B explain the absolute hydration heat values for HT-B being 2-3 times that of HT-D at the corresponding temperature of dehydration.

It appears that HT-B is attractive as a heat exchanger due to the large hydration heat values, namely 398±4 and 508±10 Jg^-1, at low dehydration temperatures (70 and 110^oC), good reproducible stability in repeated dehydration, and very quick response for water vapor absorption (4 min). The hydration heat of HT-B at 70^oC temperature is rather larger than that of other sorbents (dehydrated at 80^oC) like Mg-exchanged clinoptilolite (220 Jg^-1) and Mg-exchanged A type zeolite (393 Jg^-1).

19. Electrochemically induced transport processes in basaltic and rhyolitic melts (N. Zidarov, J. Muchovski, M. Tarassov, N. Zotov)

The investigation of ion-transport in anhydrous basaltic melts upon electric field with constant intensity, E, in air were continued [53]. A comparative analysis of experiments where the melt was imposed for 24 hours at 1330°C and electric field of moderate (0.34 V/cm) and high (1.74 V/cm) intensity with respect to a referent melt (E=0) is accomplished. The results from the obtained color maps and concentration profiles of the melt constituents (see the Figure) show that the longitudinal distribution for all the elements are esencially uniform within the limits of the statistical error up to the so called "cathodic region", except for that near to sample's bottom, spreading over a distance of 1mm far from the cathodic surface. When the melt is imposed to a high-intensity electric field significant alterations of the concentration are observed within the "cathodic region" of both the upper (profile 1) and the middle (profile 2) part of the melt. For the framework forming elements (Si, Al, and Ti) these alterations are minimum along the constitutional profiles. The lower the mean concentration of the corresponding element the less pronounced is this minimum near to the anode. For Ca, Fe, Mg, Na and K, determining the ion-current and acting as structure modifiers, the concentration alterations are manifested as carriers of positive gradients (increasing concentration of Ca and Mg) and of negative gradients (decreasing concentration of Na and K), while for Fe the constitutional profile maximizes near the middle of the "cathodic region".

Near to the bottom of the sample all constitutional profiles, especially those for the elements with higher mean concentration (Si, Al, Ca, Fe and Mg), undergo significant changes over the whole sample's length (profile 3), due most probably to an appreciable distortion of the imposed electric field.

The general trends in the longitudinal constitutional profiles within the "cathodic region" suggest that the absolute value of their slopes decreases steadily toward the bottom of the sample.

In the lowest part of all samples, with or without imposed electric field, a crystalline phase, spinel of the type (Mg²⁺Fe²⁺)(Al³⁺Fe³⁺Ti⁴⁺)₃O₄, was identified. The crystals are of a cubic symmetry and are sized from 30 to 40 mm. The Fe-concentration, measured close to the crystals, is significantly lower than that in the middle part of the samples.

The results obtained for high and moderate electrolysis into basaltic melts reveal that dissociated oxygen diffusing from air reduces on the cathode together with the cations of the network-modifiers (Ca, Mg, Fe, Na and K). At sufficiently high current densities, the reduced oxide ions O^2– promote spontaneous proceding of two different types of chemical reactions in the melt: Me^O + (1/2)O₂ = Me²⁺+ O^2– and (1/2)O₂ + (Si-O-Si) + 2e = 2(Si-O). Thus, oxygen contributes actively to the re-distribution of: (1) the network modifiers, shifting the reduction potential of the couples Me²⁺/Me^O and influencing the rate of the overall electrochemical reaction; (2) the network formers Si, Al and Ti, during the depolimerization of the silicate structure. The complex effect of the electrochemical reactions, taking place before and after the chemical reactions and accompanying the transport processes, leads to more or less pronounced changes in the bulk concentration of all the melt constituents.

Under appropriate conditions at the bottom of the electrochemical cell a crystallization of spinel starts, whose composition depends on the degree of melt oversaturation, while the quantitative interrelations therein depend directly on the Fe³⁺/Fe²⁺ ratio.

IV. SYNTESYS, COMPOSITON, STRUCTURE, AND PROPERTIES OF MINERALS AND NEW MATERIALS

20. Structural state of opal in opal-siliceous rocks, Eastern Rhodopes (A. Ilieva, B. Mihailova)

The structural state of opal is studied in three samples (S1, from opaline silicites near Svetoslav village, S2 from opaline silicites near Perperek village, and S3, from opalized wood near Haskovo, S3) from opal siliceous rocks in Eastern Rhodopes using X-ray diffraction, scanning electron microscopy and vibrational spectroscopy [56].

Fig. 1. SEM micrographs of opal-CT

The XRD patterns of the samples studied show that the strongest diffraction maximum for all the three samples correspond to d-spacing of about 4.10 Е. A less intense peak is observed at 4.30 Е for samples S1 and S3, whereas only a shoulder on the low-angle side of the main maximum exists for S2. In addition, a high-angle shoulder of about 3.91 Е is observed for S1 and S3. The peak at 2.50 Е is typical of all the three opal samples, whereas an extra peak at 3.34 Е occurs only in the pattern of S1. According to the accepted classification, the XRD patterns observed are characteristic of hydrous silica microcrystalline variety opal-CT (Fig. 1.). The well-pronounced secondary peak at 4.3 Е and the shoulder near 3.9 Е indicate a high relative amount of tridymite in samples S1 and S3. The tridymitic nature of the opal-CT is most revealed in sample S3. A typical SEM-image of the samples studied is shown in the figure. The so-called lepidospheres (Fig. 1a), built up of randomly oriented blade microcrystallites (Fig. 1b), are observed. Such a morphology has been reported by many authors for opal of different genesis - deep-see cherts, opoki, agates, etc.

Sample S1 was also examined by DRIFT and FT-Raman spectroscopy. The infrared absorption data show that the dominant phase in this opal sample is tridymite, although a small amount of amorphous silica may exist. The Raman spectroscopy method provides more information on the local structure of opal-CT. The weak Raman signal near 495 cm^-1 (typical of vitreous silica) in the spectrum of S1 shows that on the length scale of a few unit cells, the degree of crystallinity of S1 is high. The Raman scattering at 462 and near 425 cm^-1 indicates the presence of quartz and a-cristobalite, respectively. The Raman spectra of different tridymite samples may substantially differ from each other but, a strong Raman scattering between 403 and 300 cm^-1 was always observed. Our data show that the Si-O network of tridimite involves a substantuial amount of five-membered rings, probablly formed in the vicinity of structural defects such as dislocations, cavities and openings sized about several Е.

21. Viscosity of solutions in the region of crystallization of cesium-lithium borate (D. Shumov, A. Nenov, V. Nikolov)

Cesium-lithium borate (CLBO) is one of the most perspective materials for non-lineal optical applications, characterized with a complex of appropriate thermal, physical, and optical properties. One of the main problems in growing of single crystals of this material is the low rate of growth and the defects related to the high viscosity of the solutions used.

On the basis of preliminary studies concerning the crystallization of CLBO, this investigation was aimed at following the change in the solution viscosity in this range in order to choose the most suitable initial solution for growing single crystals. The dynamic viscosity was measured along eight directions starting from the stoichiometric (st.) composition CsLiB₆O₁₀ and directed in the diagram so that to follow the change in the solution initial composition in the course of the crystal growth. These directions were chosen in such a way that to follow the effect of each component on the viscosity (see the Figure). It is seen that the eighth directions studied can formally be classified in two groups. The solutions along 3, 5, and 7 are of a relatively low viscosity (about 10 P), which does not change with variations in the solvent composition and the saturation temperature. It should be noted that these are solutions in which the content of Li₂O is equal to or excedes the stoichiometric one and increases along the ray direction. Evidently, the expected rise of viscosity with decreasing temperature is compensated by its decrease with increasing the content of Li₂O.

Fig. 1. Variation of the dynamic viscosity as a function of the solution composition and of the saturation temperature.

The solutions along rays 4, 6, and 8 are of an extremely high viscosity, the latter being sharply increased with varying the composition (from 70 to 240 P). These are solutions for which the content of Li₂O₃ decreases, i.e. the relative content of B₂O₃ and Cs₂O is increased. Obviously, in this case the effect of temperature increase overlaps with the rise of the content of B₂O₃and the increase in the viscosity is well pronounced. The results obtained clearly show that Li₂O strongly reduces the viscosity, Cs₂O does not affect it while B₂O₃ leads to its strong increase. From the view point of growth of single crystals of CLBO the results show that the best initial composition can be chosen to be closest to the stoichiometric one, to have stoichiometric content of B₂O₃ and to be with rising Li₂O content during the growth.

22. Crystallographic investigation of "aerinite" ( D. Nihtianova, U. Kolb, I. Queralt)

Aerinite is a mineral substance traditionally used as a blue pigment in the most famous Catalan romanic paintings between the XI - XV centuries. However, its description as a mineral is not yet completely accepted, because there have not been found crystals large enough for structural determination. Futhermore, aerinite is always found in mixtures with other minerals and pure specimens are difficult to be obtained.

A reasonable structural model of the fibrous aluminosilicate "aerinite" has been derived by applying "direct methods" to powder X -ray intensity data with a resolution of 1.80 Е and subsequent refinement. The following data were obtained: a = 16.872(1) Е, c = 5.2256(5) Е, V = 1288 Е³, space group P3c1 (or P3), formula per unit cell [Si_13.5Al_4.5O₄₂](Fe²⁺.Fe³⁺.Al)₃Mg₃ (Ca.Na)₄(OH)₆.11.3H₂ O. The structure is represented by six pyroxene-like silicate chains joined together by AlO₄ chains to form filled tube - like units. Besides, the AlO₄ chains interconnect these tube - like units. There are three different structural sites, M1 (Fe.Al), M2 (Mg) and M3 (Ca) inside the tubes, and in the middle of each tube a column of empty face-sharing hydroxyl octahedron exists. Two additional water molecules, one directly bound to Al and the other between the three metal sites, form a complex H-bond network necessary for stabilizing the structure. To simplify the structure refinement, a P6₃cm space group has been assumed, i.e. M1 and M2 are symmetrically equivalent. Inspection of the E maps obtained by direct methods shows that the disorder is mostly concentrated on one of the two symmetrically independent pyroxene chains.

In order to get additional information on the structure of this mineral we investigated it by transmission electron microscopy (SAED, Tecnai F30 ST). Several crystallographic zone axes were registered: [021], [011], [116], [112], [121], [130], [113], [122] and [114]. The theoretical SAED patterns were calculated by the program CERIUS 4.0 and were compared with the experimental transmission electron diffraction data and a good accordance is found. These different zone axes confirm unambiguosly the known X -ray powder diffraction data.

23. Orientation-dependent formation of macropores on electrochemically etched silicon surfaces (V. Dimov, P. Vitanov, N. Khaltakova, V. Gancheva)

In preparing porous silicon differently shaped micropores can be observed depending on the crystallographic orientation of the surface. Rectangular pores are formed on the (100) surfaces, while triangular on the (111) ones. These results are discussed on the basis of computer simulations.

A strong dependence of the micropore form on the crystal orientation is observed for different crystallographic planes. It is demonstrated by computer simulation that the form of pores depends on the atomic density and positions in the structure. The models are applicable to explaining the surface morphology of silicon pores formed as a result of etching along different crystallographic orientations. This result is of importance to describe the selective distribution of pores and to specify the mechanism of their formation [47].

24. Vibration and electron states in defected complex materials (L. Konstantinov, B. Mihailova, E. Dinolova)

The local structure and the phase transition process from amorphous to crystalline state in self-bonded zeolite Beta spheres are investigated using Raman spectroscopy [39]. Aging effects on the solidification process of silicalite-1 as well as the atomic interactions between nano-particles and the organic template molecules in the synthesis solutions are also studied by Raman spectroscopy [13].

It is shown on the basis of infrared absorption and Raman scattering spectroscopic measurements (Fig. 1.) that small changes in the concentration of Ca and F in the synthesis solution affect substantially the structure of the starting amorphous phases and, thus, the phase composition of the final sintered product of calcium phosphate bio-ceramics used in medicine. The addition of Ca²⁺ ions to the solution changes the degree of disorder in the structure of starting materials and enlarges the amount of hydroxyapatite in the final product. On the other hand, the addition of F^- ions strengthens P-O bonds (force constants) in the starting material and also enlarges the amount of hydroxyapatite [14].

The structure modification near the domain walls in ferroelastic lead phosphate is studied by micro-Raman spectroscopy. The differences observed between the spectra of untwinned and twinned regions of the monoclinic phase are analyzed of the basis of calculated vibrational modes of structural units with different atomic configurations and the atomic structure of the domain walls is modeled. It is shown that in the vicinity of the domain walls the displacements of lead atoms correlate preferably in planes paralleling the cleavage plane [16].

Sintered B₄C-V₂B₅ and B₄C-W₂B₅ ceramics with differing contents of metal borides are studied by powder X-ray diffraction, scanning electron microscopy and Raman spectroscopy. The results obtained indicate that metal cations replace a part of boron atoms in icosahedral positions (Fig. 2.), thus improving the micro-hardness and the wear resistance of boron carbide ceramics. It is shown that some excess carbon forms partially disordered phases between the crystallites in the ceramics, thus preventing their enlargement [33].

Fig. 1. A Raman spectrum of calcium phosphate precursor. The most intense Raman signals resulting from crystalline (cr) and amorphous (am) phases are marked by arrows.

Fig.2. A structural unit typical of B₄C

25. Synthesis, X-ray structure determination and systematic relationships of metal hydrogensquarates (T. Todorov)

Hydrogensquarates are of growing interest because of their unique chemical and crystal properties. Seven new compounds of M²⁺(HC₄O₄)₂ .nH₂O type as well as two organic complexes were studied.

All the inorganic salts studied were prepared in de-ionized water from MCO₃ (M = Mg, Ca, Sr, Ba), CdO in ratio 1:2, necessary for obtaining the corresponding acid salts. Hot solutions are cooled slowly down to room temperature in open vessels.

All the compounds investigated crystallize in the form of colorless prismatic crystals. Single crystals suitable for X-ray structure analysis were grown for the following compounds: Sr(HC₄O₄)₂.5H₂O ; Mg(HC₄O₄)₂.4H₂O ; Cd(HC₄O₄)₂.4H₂O ; Ca(HC₄O₄)₂.3H₂O ; Ba(HC₄O₄)₂.3H₂O ; 1(-) nicotinium bis(hydrogensquarate); 4-dimethylaminopyridinium hydrogensquarate.

All experiments were carried out on a Rigaku AFC5R diffractometer at the Okayama University, Japan.

The single crystal X-ray structure analysis proves that Mg(HC₄O₄)₂ .4H₂O is an acid salt the main structural unit being a magnesium disquarate complex. The coordination of the Mg atom can be described as a relatively regular octahedron built up of two oxygen atoms belonging to hydrogensquarate(-) anions in transconfiguration and four oxygen atoms from water molecules. The Mg-O distance is in the range of 2.041(2) - 2.107(2) Е and the angle О-Mg-О is between 88.69(6) and 91.31(6)°. The bonds C-C and C-O are in the typical for this class of salts interveals 1.430(2) - 1.483(3) Е and 1.238(2) - 1.268(2) Е, respectively. The values given above indicate the presence of a markedly expressed electron delocalization.

In this structure H-atoms from the hydrogensquarate ions form two short and, consequently, relatively strong hydrogen bonds with O...O distances of 2.451(3) and 2.473(3) Е through which the main structural motif forms layers and chains. There are also a strongly branched set of weaker hydrogen bonds with O...O distances between 2.706(2) and 2.927(2) Е, which strengthen the three dimensional structure.

The preliminary processing of the intensity data for Cd(HC₄O₄)₂ .4H₂O and the calculated unit cell parameters proved that Cd(HC₄O₄)₂ .4H₂O and Mg(HC₄O₄)₂ .4H₂O are isomorphous.

The acid salt 4-Dimethylaminopyridinium hydrogensquarate forms through transfer of one of the hydrogen atoms from the squaric acid molecule to the hetero-N atom in 4-Dimethylaminopyridine. This compound is the main building unit in which an intramolecular hydrogen bond of N-O...O type with N…O distance of 2.688(5) Е is observed. The N-C distances are 1.347(5) Е and 1.340(5)Е, while the C-C distances are in the usual range of 1.320(6)-1.433(5) Е. The geometry parameters of the hydrogensquarate ion does not reveal any pecculiarities differing from the corresponding ions in the metal complexes. The main structural unit forms layers through relatively strong O-H…O hydrogen bonds with O…O distance of 2.518(4) Е. These layers coincide with the (111) planes and are distanced at 3.5 Е from each other, this distance being determined mainly by steric factors.

26. Crystal structure of bis(phenylguanidinium) carbonate monohydrate (T. Todorov, R. Petrova)

The crystal structure of bis(phenylguanidinium) carbonate monohydrate was solved using single crystal structure analysis [10] on crystals grown in the Institute of Organic Chemistry - BAS.

In this compound, 2C₆H₅NHC(NH₂)₂⁺ .CO₃ .H₂O, the phenylguanidinium cations and carbonate anions are arranged to form planes parallel to bc. The water molecules are located between these planes. The tree-dimensional packing of structural units is stabilized by complex network of hydrogen bonds.

There are two independent phenylguanidinium cations in this structure, Phg1 and Phg2, with differing geometries in respect to the position of the phenyl and guanidine groups. The torsion angles C1-N13-C11-C16 and C2-N23-C21-C26 are equal to 54.4(2)° and 79.7(2)°, respectively.

The phenyl groups of the Phg1 cations are parallel to each other and form a hydrophobic layer paralleling bc. The Phg2 molecules and carbonate anions are located on both sides of the layers while the water molecules fill the space in-between. The hydrogen atoms of the guanidinium groups and the water molecules take part in an extensive network of hydrogen bonds, connecting the layers in the c direction.

The conformational non-equivalence of both cations, described above is due to the different hydrogen-bond systems involving atoms N12 and N21, as the only conformational freedom of the phenylguanidinium cation is rotation with respect to the bond N(guan)-C(phen). While the group Phg1 forms hydrogen bonds with the carbonate oxygen atoms, the group Phg2 is connected by hydrogen bonds only with e water molecules.

This is the reason the phenylguanidinium cation conformation to be strongly dependent on its environment.

27. Synthesis of cyclic alkilene carbonates. Mechanism of interaction of carbon dioxide with oxiranes (K. Kosev, K. Troev)

The synthesis of 4-substituted 1,3-dioxolan-2-ones resulting from the interaction between carbon dioxide and oxiranes in the presence of a catalytic system composed of tetraalkylammonium or phosphonium halide and calcium chloride is investigated. It is established that calcium chloride enhances the catalytic activity of the onium halides used. A mechanism describing the interaction between carbon dioxide and oxiranes is suggested on the basis of the obtained experimental data. According to the assumed mechanism the catalytic system activates the oxirane and the opening of the oxirane ring is the rate determinig stage [11].

V. Ph.D. THESISES

28. Alteration of scheelite and formation of secondary tungsten and tungsten-iron minerals under supergene conditions (M. Tarassov)

The chemical and structural evolution of tungsten and tungsten-ferric iron minerals in the supergene zone of scheelite-sulphide deposits is studied on the basis of Grantcharitza scheelite-pyrite deposit, Bulgaria. Natural and synthetic samples are studied using experimental modelling of exogene processes, thermodynamic analysis of phase equilibria, modelling of structure and phase conversion, and a complex of analytical methods such as SEM, TEM, powder X-ray diffraction, and Raman spectroscopy. The most important results are concerned with: (1) the mechanisms of scheelite alteration; (2) the formation of equilibrium and non-equilibrium phases in the system WO₃-Fe₂O₃-H₂ O; (3) the incorporation of tungsten in ferric iron oxide/hydroxide minerals. It is shown that the phases WO₃.2H₂O (below 50^oC), WO₃.H₂O (between 50 and 120^oC), and WO₃.1/3H₂O (above 120^oC) are equilibrium products of the scheelite decomposition in H₂SO₄ solutions (pH ~ 0,5-2,0). The processes of Ca²⁺ to H⁺ ion exchange in the solid surface, the topotactical transformation of residual W-O skeleton into a new phase (WO₃.1/3H₂O ), and the dissolution-crystallization leading to formation of WO₃.2H₂O, WO₃.H₂O, and WO₃.1/3H₂O are found to proceed during the alteration of scheelite in H₂SO₄ solutions. All these processes take place under supergene conditions forming both WO₃.nH₂O (n=2 for hydrotungstite and n=1 for tungstite) as a result of dissolution-crystallization, and WO₃.xFe₂O₃.nH₂O poorly crystallized ochre, a natural analogue of WO₃.1/3H₂O, resulting from a combination of dissolution-precipitation and solid state process. It is established that the equilibrium WO₃.xFe₂O₃.nH₂O mineral [ferritungstite, (W,Fe)(O,OH)₃] is neither a product of direct crystallization from W- and Fe-containing solutions nor an ultimate product of the structural evolution of disordered WO₃.xFe₂O₃.nH₂O gels. Synthetic analogues of ferritungstite were obtained only using metasomatic schemes of alteration of crystalline WO₃.nH₂O phases and WO₃.xFe₂O₃.nH₂O gels. The atomic ratio Fe/W in (W,Fe)(O,OH)₃ phase is found to depend on the ratio Fe/W, pH of the aqueous solutions, and on the chemical composition of the solid precursor. The investigation of compact W-containing goethite shows that the material is composed of nearly pure goethite microcrystals (W/Fe<0,006) cemented by Fe₂O₃.yWO₃.nH₂O gel, which resembles the structure of ferrihydrite or goethite.

INTERINSTITUTES PROGRAMS:

Gold based catalysts for environmental important reactions. Interinstitute project with University of Ghent, Belgium (Collaborative linkage grant, NATO Scientific Affairs Division)

POSTDOCTORAL FELLOWS AND VISITING SCIENTISTS:

Dr. Boriana Mihailova - Hamburg University (Humboldt's Grant), Germany
Dr. Nadya Petrova - Ube University, Japan
Dr. Stanislav Vassilev - National Institute of coal, Oviedo, Spain
Dr. Todor Todorov - University of Okayama, Japan
Dr. Yuri Kalvachev - Leipzig University (Humboldt's Grand), Germany
Dr. Diana Nihtianova - Johannes Gutenberg University, Mainz, Germany

AWARDS

Assoc. Prof. Bogdana Zidarova, DSc, was awarded by the Bulgarian Scientific-Technical Unions a "Prof. A. Zlatarov" prize for high scientific-technical achievments.

PUBLICATIONS AND REPORTS AT CONFERENCES AND LOCAL MEETINGS:

PUBLISHED ARTICLES AND REPORTS:

1. Banushev, B., Z. Tsintsov, D. Stoyanov. 2001. Silicified tuffs from the Kurdjali region. – Mining and Geology, 3, 34-38. (in Bulgarian with English abstracts)

2. Bonchev, P., I. Pancheva, T. Todorov, D. Mehandjiev, N. Savov. 2001. Complexation of the antihypertensive drug oxprenolol with copper (II). - J. Inorganic Biochemistry, 83, 25-30.

3. Georgieva, R., R. Tcevi, K. Kossev, M. Baldgjiska, R. Petrova, V. Tenchova, I. Gitcov, K. Troev. 2001. Immobilization of aminothiols on poly (ethylene phosphates). Formation of poly (ethylene phosphates)/cysteamine complexes and their radioprotective efficiency. - J. of Medicinal Chemistry,

4. Damyanov, Z., M. Vassileva. 2001. Authigenic phyllosilicates in the Middle Triassic Kremikovtsi sedimentary exhalative siderite iron formation, Western Balkan, Bulgaria. – Clays and Clay Minerals, 49, 6, 559-585.

5. Damyanov, Z., M. Vassileva, J. Kortenski, A. Sotirov. 2001. Petrology of the organic matter in the Kremikovtsi siderite iron formation, West Balkan Moutain, Bulgaria. – In: Eighteenth Annual Meeting of the Society for Organic Petrology, Ext. Abstracts, 23-26 September, Houston, Texas, USA, vol.18, 36-40.

6. Dekov, V., Z. Damyanov, G. Kamenov, I. Bonev, I. Rajta, G. Grime. 2001. Sorosite (h-Cu₆Sn₅) – bearing native tin and lead assemblage from the Mir zone (Mid-Atlantic Ridge, 26⁰N). – Oceanologica Acta, 24, 3, 205-220.

7. Donchev, I., A. Lenchev, J. Ninov, L. Gigova. 2001. Study of some mineral and technological properties of fly-ashes from thermoelectric power stations Republika and Bobovdol, Bulgaria. - Compt. rend. Acad. bulg. Sci., 54, 11, 75-80.

8. Kamenov, B., E. Tarassova, R. Nedialkov, B. Amov, P. Monchev, B. Mavroudchiev. 2000. New radiometric data from Late Cretaceous pluton in Eastern Srednogorie area, Bulgaria. – Geochem., miner. and petrol., 37, 5-24.

9. Kashino, S., T. Mitsuro, T. Todorov. 2001. 2,2 – Dihydroxychalcone. - Acta Crystallographica, E 58, 735 - 737.

10. Kolev, Ts., T. Todorov, R. Petrova. 2001. Bis (phenylguandinium) carbonate monohydrate. - Acta Crystallographica, E 57, 1-3.

11. Kossev, K., N. Koseva, K. Troev. 2001. Synthesis of cyclic alkylene carbonates I. Mechanism of the reaction of oxiranes with carbon dioxide. - Bull. Chem. Soc. Japan,

12. Kotsilkova, R., V. Petkova, Y. Pelovski. 2001.Thermal analysis of polymer-silicate nanocomposites. - Journal of Thermal Analysis and Calorimetry, v. 64, 591-598.

13. Li, Q., B.Mihailova, D. Creaser, J. Sterte. 2001. Aging effects on the nucleation and crystallization kinetics of colloidal TPA-silicalite-1. - Microporous and Mesoporous Materials, 43, 51-59.

14. Mihailova, B., B. Kolev, Ch. Balarew, E. Dulgerova, L. Konstantinov. 2001. Vibrational spectroscopic study of hydrolysed starting materials for preparation of calcium phosphate bio-ceramics. - Journal of Materials Science, 36, 4291-4297.

15. Mihailova, B., L. Konstantinov. 2001. Raman spectroscopy as a method for structural investigations in nanometric scale.- Proceeding 3^rd workshop on Nanoscience &Nanotechnology, 30 Nov. - 1 Dec., Sofia, Bulgaria.

16. Mihailova, B., U. Bismayer, A. Engelhardt, B. G?tler. 2001. Wall-related Raman scatering in ferroelastic lead phosphate Pb₃(PO₄)₂. - Journal of phisics: Condensed Matter, 13, 9383-9392.

17. Mintova, S., Th. Bein. 2001. Microporous films prepared by spin-coating stable colloidal suspensions of zeolites. - Advanced Materials, 13, 24, 1880-1883.

18. Mintova, S., Th. Bein. 2001. Nanosized zeolite films for vapor-sensing applications. - Microporous and Mesoporous Materials, 50, 2-3, 159-166.

19. Mintova, S., N. Petkov, K. Karaghiosoff, Th. Bein. 2001. Transformation of amorphous silica colloids to nanosized MEL zeolite. - Microporous and Mesoporous Materials, 50, 2-3, 121-128.

20. Mintova, S., B. Stein, J. Reder, Th. Bein, 2001. Synthesis and characterization of microporous titanium-silicate materials. - Studies in Surface Science and Catalysis, 135, (Zeolites and Mesoporous Materials at the Dawn of the 21^st Century), 1702-1709.

21. Mintova, S., J. Visser, Th. Bein. 2001. Preparation of microcalorimetric gas sensors with CoAPO-5. - Studies in Surface Science and Catalysis, 135, (Zeolites and Mesoporous Materials at the Dawn of the 21^st Century), 3495-3502.

22. Mintova, S., T. Metzger, Th. Bein. 2001. Depth-sensitive structural study of silicalite-1 films with grazing incidence X-ray diffraction. - Studies in Surface Science and Catalysis, 135, (Zeolites and Mesoporous Materials at the Dawn of the 21^st Century), 3160-3167.

23. Metzger, T., S. Mintova, Th. Bein. 2001. Nanoscale crystal orientation in silicalite-1 films studied by grazing incidence X-ray diffraction. - Microporous and Mesoporous Materials, 43, 2, 191-200.

24. Mintova, S., Sh. Mo, Th. Bein. 2001. Humidity sensing with ultrathin LTA-type molecular sieve films grown on piezoelectric devices. - Chem. Mater., 13, 3, 901-905.

25. Mizota, T., N. Petrova, N. Nakayama. 2001. Entropy of zeolitic water. - J. Thermal Analysis and Calorimetry, 64, 211-217.

26. Pecskay, Z., A. Harkovska, N. Zidarov, M. Popov, V. Panteva. 2001. K-Ar dating of the tertiary volcanic rocks from Ograzden and Maleshevska Mountains, South-Western Bulgaria. – Compt.rend.Acad.bulg.Sci., 54, 4, 71-76.

27. Pelovski, Y., Iv. Dombalov, V. Petkova. 2001. Mechanical triboactivation of dolomite. - Journal of Thermal Analysis and Calorimetry, v. 64, 1257-1263.

28. Petkova, V., Y. Pelovski. 2001. Investigation on the thermal properties of Fe₂O(SO₄)₂. Part I. - Journal of Thermal Analysis and Calorimetry, v. 64, 1025-1035.

29. Petkova, V.,Y. Pelovski. 2001. Investigation on the thermal properties of Fe₂O(SO₄)₂. Part II. - Journal of Thermal Analysis and Calorimetry, v. 64, 1037-1044.

30. Petrov, O., E. Dyulgerova, L. Petrov, R. Popova. 2001. Characterization of calcium phosphate phases obtained during the preparation of sintered biphase Ca-P ceramics. - Materials Letters, 48, 162-167.

31. Petrova, N., T. Mizota, Ts. Stanimirova, G.N. Kirov. 2001. Hydration enthalpy of hydrotalcite low-temperature metaphases. - J. Mineral. Petrol. Sci,

32. Petrova, N., T. Mizota, K. Fujiwara. 2001. Hydration heats of zeolites for evaluation as heat exchangers. - J. Thermal Analysis and Calorimetry, 64, 157-166.

33. Radev, D. D., B. Mihailova, L. Konstantinov. 2001. Raman spectroscopic study of metal-containing boron carbide-based ceramics. - Solid state Sciences,

34. Starbova, K., V. Mankov, N. Starbov, D. Popov, D. Nihtianova, K. Kolev, L. Laude. 2001. Phase transitions in excimer laser irradiated zirconia thin films. - Applied Surface Science, 173, 177 - 183.

35. Schoeman, B., E. Babouchkina, S. Mintova, V. Valtchev, J. Sterte. 2001. The synthesis of discrete colloidal crystals of zeolite beta and their application in the preparation of thin microporous films. - J. Porous Mater., 8, 1, 13-22.

36. Tarassov, M. 2001. Alteration of scheelite and formation of secondary tungsten and tungsten-iron minerals under supergene conditions. (Ph.D. thesis)

37. Tarassova, E., P. Petrov. 2001. Ore mineralizations related to the Oman-Fakija pluton, Eastern Srednogorie. – Mining and Geology, 3, 39-44. (in Bulgarian with English abstracts)

38. Tarassova, E., N. Zidarov, N. Khaltakova. 2001. I-type granitoids from Belassitza Mountain, SW Bulgaria. – Ceochem., miner. and petrol., 38, 79-88.

39. Tosheva, L., B. Mihailova, V. Valtchev, J. Sterte. 2001. Zeolite Beta spheres. - Microporous and Mesoporous Materials, 48 , 31-37.

40. Tsanov, T., K. Kossev. 2001. Practical application of modified poly (ethylene oxide). - Networks, Reactive and Functuonal Polymers, 50, 3, 243-255.

41. Tsintsov, Z. 2001. Genetically indicative features of Pt-Fe and Os-Ir-Ru alloy crystals from placers in SW Bulgaria. – Geochem., miner. and petrol., 38, 35-44.

42. Tsintsov, Z., B. Banushev, R. Pazderov. 2001. Mineralogical Characteristic of Paleogene coral agates from Eastern Rhodopes, Bulgaria. – N. Jb. Miner. Mh., 10, 464-480.

43. Valtchev, V., S Mintova. 2001. Layer-by-layer preparation of zeolite coatings of nanosized crystals. - Microporous Mesoporous Mater., 43, 1, 41-49.

44. Vassilev, S., G. Eskenazy, C. Vassileva. 2001. Behaviour of elements and minerals during preparation and combustion of the Pernik coal, Bulgaria. - Fuel Processing Technology, 72, 103-129.

45. Vassilev, S., R. Menendez, D. Alvarez, A. Borrego. 2001. Multicomponent utilization of fly ash: dream or reality. - Proceedings of the International Ash Utilization Symposium, Lexington, KY, USA, 22-24 October, 20 p.

46. Vassileva, B., O. Petrov, S. Hammad. 2001. Effect of natural sorbents during clean-up of cation polluted water: I. An example on Egyptian bentonite - Bulgarian clinoptilolite filter. - Compt. rend. Acad. bulg. Sci., 54, 12, 63-66.

47. Vitanov, P., V. Dimov, N. Khaltakova, V. Gancheva. 2001.Orientation dependent formation of macropores by silicon surface electrochemical etching. – Proceedings of the 11^th Int. Sc. on Cond. Mat. Phys., ISCMP, Varna, 2000, 284-287.

48. Vitov, O., 2001. Placer mineralogical map of Bulgaria. – Geology and Mineral Resourses, 9, 19-22 (in Bulgarian with English abstract)

49. Vitov, O., I. Marinova. 2001. Periodicity of gold concentrations from secondary dispersion aureoles in the Western Srednogorie. – Compt.rend.Acad.bulg.Sci., 54, 5, 53-58.

50. Vitov, O., L. Konstantinov. 2001. Method for determining the cleavability of fluorite. – Compt.rend.Acad.bulg.Sci., 54, 3, 55-58.

51. Zhelyaskova-Panayotov?, ?., Z. Tsintsov, G. Pashov. 2001. Hydrothermal gold mineralization in ultrabasites near Dobromirtsi village, Kurdjali region. – Ann. Univ. Sof., v.1 – geologia, t. 93, 173-186. (in Bulgarian with English abstracts)

52. Zidarov, N. 2001. Central Laboratory of Mineralogy and Crystallography, Bulgarian Academy of Sciences, and the challenges of the new time. – ?ining and Geology, 9, 38-41. (in Bulgarian with English abstracts)

53. Zidarov, N., J. Mouchovski, M. Marinov, M. Tarassov, N. Zotov. 2001. Ion-mass transport in anhydrous basaltic melts in an electric field. – Chemical Geology, 174, 51-61.

PUBLICATIONS IN PRESS:

54. Donchev, I., A. Lenchev, J. Ninov, L. Gigova. 2002. Possibilities for utilization of fly ashes from TEPS as an additive to clinker for portland cement production. - 40 year Jubilee proceedings of Plovdiv University.

55. Eskenazy, G., S. Vassilev. 2002. Geochemistry of chlorine and bromine in Bulgarian coals. – Rev. Bulg Geol. Soc.,

56. Ilieva, A., B. Mihailova. 2002. Structural state of opal siliceous rocks, Eastern Rhodoeps. - Compt. rend. Acad. bulg. Sci., 55, 2, 65-70.

57. Kostov-Kytin, V., S. Ferdov. 2002. Invetigations in the system Na₂O-K₂O-TiO₂-SiO₂ H₂O. - Compt. rend. Acad. bulg. Sci., 55, 1, 51-54.

58. Kostov-Kytin, V., S. Ferdov, O. Petrov. 2002. Hydrothermal synthesis and successive transformation of paranatisite into natisite. - Compt. rend. Acad. bulg. Sci., 55, 2, 61-64.

59. Penev, V., N. Zidarov, B. Zidarova. 2002. Geometrization of the language of mineralogy: Formulation of the problem and outlining the way of its solution. – Compt.rend. Acad. bulg.Sci., 55, 5,

60. Tzvetanova, Y. 2002. Garnet-Pyroxene skarns from Zvezdel pluton (East Rhodopes, Bulgaria). – Compt.rend.Acad.bulg.Sci., 55, 5.

61. Vassileva, C., S. Vassilev. 2002. Relation between ash-fusion temperatures and chemical and mineral composition of some bulgarian coals. – Compt.rend.Acad.bulg.Sci., 55,

62. Vassileva, C., S. Vassilev. 2002. General observation on the phase-mineral transformation in inorganic matter of some bulgarian coals during heating. – Compt. rend. Acad. bulg. Sci., 55,

63. Vitov, O. 2002. Indications of cassiterite mineralizations in Bulgaria. – Mining and Geology, 3,

64. Zidarova, B., M. Marinov, N. Zidarov. 2002. Mathematical model for the growth of fluorite aggregates in caverns in Slavyanka deposit. – Compt.rend.Acad.bulg.Sci., 55, 3, 59-64.

ABSTRACTS AND POSTERS AT SCIENTIFIC EVENTS:

65. Bismayer, U., B. Mihailova. 2001. Ferroelastic domains: synchrotron and inelastic liht scattering studies. - 20^th European Crystallographic Meeting, 25-31 August, Krkow, Poland.

66. Damyanov, Z., M. Vassileva, J. Kortenski, A. Sotirov. 2001. Petrology of the organic matter in the Kremikovtsi siderite iron formation, West Balkan Moutain, Bulgaria. – In: Eighteenth Annual Meeting of the Society for Organic Petrology, Ext. Abstracts and Program, 23-26 September, Houston, Texas, USA, vol.18, 36-40.

67. Gasharova, B., B. Mihailova, J. G?ttlicher 2001. X-ray diffraction and Raman spectroscopy study of KFe₃(CrO₄)₂(OH)₆ and (H₃O)Fe₃(SO₄)₂(OH)₆. - 9^th Meet. of German Soc. of Crystallogrphy, 12-15 March, Bayreuth, Germany.

68. Mihailova, B., U. Bismayer, A. Engelhardt, B. G?ttler. 2001. Domain wall effects on the optical phonons in ferroelastic lead phosphate Pb₃(PO₄)₂. - European Crystallographic Meeting, 25-31 August, Krakow, Poland.

69. Mihailova, B., U. Bismayer, B. Guttler, L. Tosheva, J. Sterte. 2001. Disorder-indused Raman scattering in defect crystals. - Workshop "Recent research activities in lihgt scattering techniques", 22-24 Sept., Hamburg, Germany.

70. Petrova, N., T. Mizota, Ts. Stanimirova, G. Kirov. 2001. Hydration enthalpy of thermally treated hydrotalcite. - The Mining and Materials Processing Institute of Japan, 29-31 March,Tokyo, 204-205.

71. Tarassov, M. 2001. X-ray amorphous and crystalline ferric iron tungsten oxide phases from Grantcharitza tungsten deposit, Bulgaria. - Proceedings of the International Seminar "Non-Crystalline State of Solid Mineral Matter", 19-21 June, Syktyvkar, Rep. Komi, Russia, Part 3, 103-105.

72. Fujiwara, K., Y. Hara, T. Mizota, N. Nakayama, N. Petrova. 2001. Preparation and hydration heat properties of H-type zeolites. - The Mining and Materials Processing Institute of Japan, 29-31 March, Tokyo, 206-207.

73. Vassilev, S., R. Menendez, D. Alvarez, A. Borrego. 2001. Multicomponent utilization of fly ash: dream or reality. - Proceedings of the International Ash Utilization Symposium, 22-24 October, Lexington, KY, USA, 20 p.

74. Donchev, I., A. Lenchev, J. Ninov, L. Gigova 2001. Possibilities for utilization of fly ashes as anadditive to clinker for portlandcement production. - 40 year Jubilee proceedings of Plovdiv University.

PAPERS PRESENTED ON THE POSTER SESSION
“SCIENTIFIC AND APPLIED ACHIEVEMENT OF CLMC, BAS”
19 MAY 2001

75. Geogenetic models of deposits in the Fluorite formation. - B. Zidarova, N. Zidarov.

76. Application of mineralogical methods for prospecting of fluorite ore. - B. Zidarova.

77. Geogenetic model of the primary ore formation in Kremikovtsi deposit. - Z. Damyanov.

78. Criterions for search of polymetal-barite-iron ore stratiform deposits ("Kremikovtsi type") in carbonate rocks from the Western Balkan - Z. Damyanov.

79. A fragment from a Proterozoic oceanic crust in Ograzden mountain, Serbo-Macedonian Massif, SW Bulgarian. - N. Zidarov, P. Nenova.

80. Chemistry and polytype character of white mica: an indicator for the P-T-t evolution of metamorphic terrains (Byala reka metamorphic group, E Rhodopes). - L. Macheva.

81. Mineralogy and geochemistry of coal, waste products from TEPS and coke from hard municipal wastes. - S. Vassilev, Ch. Vassileva.

82. Mineralogical and technological studies of products from flotation of copper slags in "Union minier Pirdop copper" plant. - I. Donchev, B. Zidarova.

83. 1:25 000 mineralogical map of the heavy mineral concentrates in Bulgaria (state of investigation). - O. Vitov.

84. 1:25 000 mineralogical map of the heavy mineral concentrates in Bulgaria (gold). - O. Vitov.

85. Accessory Fe-Mn-Ti oxides in intrusive rocks - indicators for crystallization conditions and post-magmatic activity of the intrusions. - E. Tarassova.

86. Application of the mixture Na₂CO₃-ZnO for dissolution during determination of boron in tourmaline by ICP-AES analysis. - N. Lihareva.

87. Alluvial gold treasure in Bulgaria (or the inventions of the mineralogist). - Z. Tsintsov.

88. Geometrization of the foundations of chemistry. - V. Penev.

89. Mass-transport processes in dry basaltic melts in electric field. - N. Zidarov, J. Mouhovski, M. Marinov, M. Tarassov, N. Zotov.

90. Growth of ??F₂ optical crystals from Bulgarian mineral stuff with a wide spectrum of utilization. - J. Mouhovski.

91. Structure of intercalated layered silicates (PILS) - electron microscopic study and numerical modeling. - V. Dimov, A. Ilieva, N. Khaltakova, L. Filizova.

92. Investigation of the system Na₂O-K₂O-TiO₂-SiO₂ – H₂O. - V. Kostov-Kytin, O. Petrov, S. Ferdov.

93. Growth of oxide single crystals with non-linear optical properties. - D. Shumov, A. Nenov.

94. Synthesis and study of new intermediate compounds obtained during thermal decomposition of some inorganic materials. - V. Petkova.

95. Biphase calcium-phosphate bioceramics - phase composition, characteristic, properties. - O. Petrov, E. Dyulgerova, R. Popova, L. Petrov, B. Mihailova, L. Konstantinov.

96. Thermal stability and ion exchange properties of clinoptilolite from Beli plast deposit, Bulgaria. - O. Petrov.

97. Structural mechanisms of sheelite alteration in supergenic conditions. - M. Tarassov.

98. Structural study of Pb₅MoO₈ single crystals by SAED and HREM. - D. Nihtianova, V. Ivanov, V. Yamakov.

99. Adducts of urea with bivalent metal perrhenates. - T. Todorov, R. Petrova.

100. Structural classification of inorganic orthophosphates. - R. Petrova, T. Todorov.

101. Synthesis and characterization of zeolite materials. - L. Konstantinov et al.

102. Synthesis, structural and phase characterization of phytopharmaceutical preparations. - K. Kossev.

103. Sorption purification of waste water. - B. Vassileva.