We have undertaken a study of the hydrated hydroxyl carbonate mineral, hydromagnesite, from the burnt mine dump of the Mayrau coal mine at Vinařice near Kladno, central Bohemia (Czech Republic). Hydromagnesite occurs as rich white crystalline coatings up to several cm2 in size formed by spherical to hemispherical aggregates up to 0.5 mm in size. The semi-quantitative chemical analyses of hydromagnesite confirmed presence of Mg and O. Hydromagnesite is monoclinic, the space group P21/c, with the unit-cell parameters refined from X-ray powder diffraction data: a 10.096(3), b 8.934(2), c 8.366(3) Å, β 114.471(19)° and V 686.8(4) Å3. Raman spectroscopy documented the presence molecular water, hydroxyl groups and carbonate units in its crystal structure.
Argentopyrite in association with miargyrite was found on an archived specimen probably originating from the Lill shaft, Černojamské deposit (central Bohemia, Czech Republic). It was found as small wheel-like crystal aggregates up to 1 mm in size partly replaced by small crystals of pyrite. The original colour is bronze-brown but it tarnished black. Apart from main elements Ag, Fe and S, it contains minor Cu and Hg (up to 0.04 apfu) and Te. Its empirical formula (4 analyses) on the basis of 6 apfu corresponds to (Ag0.97Cu0.04)Σ1.01Fe1.93S3.06. The predominant ore mineral on the specimen is miargyrite with empirical formula Ag0.99Sb1.02S1.99 in the form of crystals up to 7 mm in size. Its colour is black and has a typical cherry-red streak. The associated minerals include siderite, sphalerite, quartz, carbonates, baryte, pyrite and possible millerite.
An unusual Mn-mineralization was found in the material from mine dump of the abandoned mine Štěstí s radostí (Glück mit Freuden) located near Ryžovna (Boží Dar), Krušné hory Mountains, Bohemia (Czech Republic). Manganite forms abundant aggregates up to 1 cm in size and veins up to 0.5 cm thick, overgrowing fragments of earlier quartz. It is usually fine-grained, the margins of the aggregates and veins are formed by tabular crystals up to 1 mm in length arranged perpendicular to the surface of the aggregates and veins. It is opaque, dark gray to blackish gray, with an earthy, silky to vitreous lustre. Manganite is monoclinic, space group P21/c, with the unit-cell parameters refined from X-ray powder diffraction data: a 5.3071(6), b 5.2743(4), c 5.3071(6) Å, β 114.456(6)° and V 135.23(3) Å3. Its chemical analyses (mean of 12 spots) correspond to the empirical formula (Mn0.97Al0.01Si0.01P0.01)Σ1.00O1.03(OH)0.97. The youngest component of the gangue is rhodochrosite, which forms aggregates up to 5 mm in size, which fill the cavities among the manganite veins. More rarely, it also forms in the cavities hemispherical aggregates up to 2 mm in size with a finely crystalline surface. In one cavity, a group of well-developed rhodochrosite crystals up to 0.25 mm in size was observed. Rhodochrosite is yellow-gray to gray, with a pink tints, it is translucent and exhibits a greasy to vitreous lustre. It is trigonal, space group R-3c, with the unit-cell parameters refined from X-ray powder diffraction data: a 4.7771(2), c 15.6687(8) Å and V 309.66(2) Å3. Its chemical composition (mean of 7 spot analyses) corresponds to the empirical formula (Mn0.95Mg0.03Ca0.02)Σ1.00CO3.
A rare mineral branchite, ideally C20H34, was discovered at the Cigeľ mine, Handlová coal deposit, Prievidza Co., Trenčín Region, Slovakia. This is the first occurrence of this relatively rare mineral in Slovakia. It occurs as colourless to white coarse crystalline fillings consisting of individual flattened aggregates up to 1 cm in size, developed in fractures of coal. The unit-cell parameters of branchite from the Cigeľ mine (for the triclinic space group P1) refined from the PXRD data are: a 11.4146(8), b 20.9692(13), c 7.4090(6) Å, α 93.945(5), β 100.732(6), γ 80.508(5)° and V 1717.2(2) Å3. The occurrence of branchite in the material from the Cigeľ mine was also confirmed by Raman and infrared spectro- scopy, and the tentative assignment of the Raman spectrum is provided in this paper.
Dawsonite, a rare sodium aluminium hydroxycarbonate, NaAl(CO3)(OH)2, was identified in material from the Tuchlovice coal mine dump in the western part of the Kladno Coal District (central Bohemia, Czech Republic). This occurrence represents the second confirmed finding of dawsonite in the Czech Republic, following its previously documented occurrence at the Slaný locality. The studied material consists of Proterozoic shales and associated quartz veins affected by superimposed hydrothermal and late-stage mineralization. Dawsonite occurs in small fractures and cavities within the shales and thin quartz veins, commonly in association with dolomite and pyrrhotite. It forms snow-white spherulitic aggregates and clusters reaching up to 1 cm in size. Dawsonite is orthorhombic, space group Imma, with the unit-cell parameters refined from X-ray powder diffraction data: a 6.7523(6), b 5.5812(5), c 10.4261(8) Å and V 392.92(4) Å3. The ED and WD analyses show substantial Na and Al contents and Raman spectrum confirms presence of (OH) and (CO3) groups in studied mineral. The mineral assemblage and host-rock characteristics suggest formation under low-temperature conditions within a CO2-rich, alkaline fluid regime comparable to that inferred for the Slaný occurrence. Due to the extensive recultivation of the dump in 2007 - 2011, further mineralogical investigation of the locality is now effectively precluded. The Tuchlovice occurrence thus provides additional insight into the distribution and paragenesis of dawsonite within the Kladno Coal Basin and confirms its rare occurrence in the Czech Republic.
The unusual find of crystallized nontronite in quartz gangue was found in the material from the exploratory trenches in the forest track “U Kutaček”, 4 km NW of Kladská in the cadastre of the town of Lázně Kynžvart (Slavkovský les Mts., Czech Republic). Nontronite occurs in cracks of quartz gangue as light yellow-green to olive green crystalline aggregates and coatings composed of thin tabular crystals on areas up to some cm2. Individual nontronite crystals with length up to 0.3 mm are light yellow-green, translucent and exhibit a vitreous lustre. Nontronite, as a member of smectite group, was confirmed by X-ray powder diffraction data. Its chemical composition (mean of 20 spot WDS analyses) corresponds to the empirical formula (Ca0.14K0.02)Σ0.16(Fe1.99Mg0.10)Σ2.09(Si3.45Al0.58)Σ4.03O10(OH)2·nH2O.
The uranium ore occurrence Novotníky near Nepomuk (western Bohemia, Czech Republic) is a small vein-type occurence hosted by quartz and quartz-carbonate veins at the contact between biotite granite and metamorphic rocks of the Central Bohemian Pluton. Primary mineralization is represented by uraninite associated with quartz, calcite and pyrite, while supergene processes led to the formation of secondary uranium minerals. New findings from shallow exploration pits (Nos. 5 - 7) document the presence of meta-autunite and phosphuranylite as the dominant supergene phases. Meta-autunite forms yellow-green tabular crystals up to 1 cm in size, whereas phosphuranylite occurs as yellow coatings, aggregates and crusts of well-developed acicular to tabular crystals up to 1 mm in size. Phosphuranylite is orthorhombic, space group Cmcm, the unit-cell parameters refined from X-ray powder diffraction data are a 15.9081(15), b 13.7415(15), c 17.325(2) Å and V 3787.2(5) Å3. Its chemical composition (mean of 14 spot analyses) based on 4 P+As+Si apfu corresponds to the empirical formula K1.10(Ca0.89Pb0.11)Σ1.00(H3O)3.43(UO2)6.81O4 [(PO4)3.76 (AsO4)0.11(SiO4)0.13]Σ4.00·8H2O. These results expand current knowledge of the supergene uranium mineralization at the uranium ore occurrence Novotníky.
New finds of primary ore mineralization in the Mikulov ore district (northern Bohemia, Czech Republic) are described in the paper. In the material from the Lehnschafter mine in Mikulov, the occurrence of arsenopyrite, chalcopyrite, galena, pyrite, sphalerite, tennantite-(Zn), as same as illite, almandine, ilmenite, TiO2 phases, xenotime-(Y), monazite-(Ce) in fragments of hydrothermally altered rocks in quartz gangue, were determined. The silver (acanthite, argentopearceite, pearceite, polybasite, proustite, stephanite) and base-metal sulfides (arsenopyrite, chalcopyrite, galena, pyrite, sphalerite) were found in the samples from mine dumps of this mine. At small mine dump in forest above the Lehnschafter mine a sample with abundant acanthite in quartz gangue was found. The occurrence of Ag minerals (silver, proustite, pyrargyrite, unknown acicular AgSbS mineral, xanthoconite, miargyrite, kenoargentotetrahedrite-(Fe), allargentum, dyscrasite) in association with galena and Sb-rich arsenopyrite was determined in quartz gangue from the gallery Dreikönig Zeche. At the Šikmá štola gallery, Ag minerals (miargyrite, kenoargentotetrahedrite-(Fe), andorite-series minerals) in association with Mn-rich berthierite, jamesonite, stibnite, antimony, galena and Sb-rich arsenopyrite in quartz gangue were found. The base-metal sulfides (arsenopyrite, galena, sphalerite) were found in quartz gangue from the gallery Štola 14 pomocníků. The descriptions and quantitative chemical composition or Raman spectra of individual mineral phases are given. The studied samples are represented by two types of mineralization, the first are base-metal sulfides in quartz gangue formed at ca. 500 - 200 °C, the second is Ag minerals in association with Sb-rich arsenopyrite, Mn-rich berthierite, rare galena, jamesonite, stibnite and antimony in quartz gangue formed by hydrothermal fluids with temperature distinctly below 200 °C.
A small feldspar pit on the Proseč Ridge near Jablonec nad Nisou (northern Bohemia, Czech Republic) exposes irregular granitic pegmatite body hosted by the Liberec Granite of the Krkonoše-Jizera Pluton. Several loose fragments containing an unusual mafic mineral aggregate enclosed in quartz-feldspar pegmatite were found in the pit. Electron-microprobe study of mafic domain revealed predominantly hedenbergite, subordinate calcic amphibole classified as potassic-hastingsite, as well as accessory titanite, fluorapatite, fluorite and chamosite. Titanite is enriched in Al and F, whereas fluorapatite is compositionally simple. Chamosite veinlets cut pyroxene and replace amphibole and document a late low-temperature hydrothermal overprint. Textural relations and mineral chemistry indicate a local Ca-Fe contamination of the pegmatite melt, followed by albitization and chloritization. The most plausible source of Ca, Fe, Mg and part of Ti, P and F was a small xenolith of calc-silicate or amphibolitic nature entrained during emplacement of the pegmatite into the granite.
Results of new electron-microprobe and sulfur isotope studies of a small vein-type Pb-Zn(-Ag) ore occurrence at Dobrá Voda near Telč are presented in this paper. The ore veins are situated at the contact of granites of the Central Moldanubian Pluton and migmatitized paragneisses of the Monotonous Group. The gangue is dominated by quartz containing small amounts of illite-muscovite, a mineral from the kaolinite group, and Fe-rich chlorite. The prevailing sulfide minerals are galena (with low contents of Ag and Sb) and sphalerite (with 0.123 - 0.175 apfu Fe, 0.004 - 0.006 apfu Cd, and 0.001 - 0.002 apfu Mn). Less frequent are pyrite and arsenopyrite, rare are microscopic grains of chalcopyrite, monoclinic pyrrhotite, kenoargentotetrahedrite-(Fe), pyrargyrite, and canfieldite. Native silver reported in literature was not confirmed. Supergene minerals are represented by acanthite, anglesite, mimetite, galena II, malachite, and smithsonite. The δ34S values of sphalerite and galena range between 2.7 and 5.4 ‰ CDT for most samples. Based on various compositional and isotope thermometers we presuppose that the main part of the studied hydrothermal mineralization originated at rather high temperatures (›ca. 300 °C). The mineral assemblage, chemical composition of minerals, and formation conditions of ore mineralization from Dobrá Voda correspond to the Freiberg-type base-metal mineralization (k-pol), widespread in the area of the Českomoravská vrchovina Mts.
As part of research on minerals of the scheelite group from Harrachov deposit (Krkonoše Mountains, Czech Republic), wulfenite, a mineral historically known but not previously studied using modern methods, was examined in detail. Two morphologically and color-wise distinct types of wulfenite were identified, whose chemical composition and X-ray diffraction data are very similar. Wulfenite I consists of orange, opaque, idiomorphic, prismatic crystals up to 1 mm in size. These crystals often grow on genetically older columnar pyromorphite crystals or on limonite or baryte. Wulfenite II consists of translucent brown, idiomorphic, dipyramidal crystals up to 1.5 mm in size. These crystals grow on tabular crystals of yellow, translucent baryte. The empirical formula of wulfenite I is Pb0.98[(MoO4)0.98(WO4)0.01]. The empirical formula of wulfenite II is Pb0.96[(MoO4)0.99(WO4)0.01]. Furthermore, imperfect gray crystals of a distinctly zoned mineral were examined, in whose zones wulfenite and stolzite with varying Mo:W ratios are gradually represented from the center to the edge. The empirical formula for all zones corresponding to stolzite is Pb1.04[(WO4)0.58(MoO4)0.42], and the empirical formula for the wulfenite zones is Pb0.99[(WO4)0.21(MoO4)0.79]. As part of this work, the chemical composition of pyromorphite was also studied; it exhibits relatively high F contents ranging from 0.27 to 0.41 apfu with empirical formula (Pb4.96Ca0.03)Σ4.99(PO4)3.00(Cl0.95F0.36)Σ1.31.
A rare hydrated barium uranyl vanadate, mineral francevillite, was found in an abandoned quarry near the village of Žinkovy in the Nepomuk region (western Bohemia, Czech Republic). Francevillite occurs as orange-yellow or bright yellow, earthy coatings and crystalline crusts formed by hemispherical aggregates up to 0.5 mm in size composed of tiny tabular crystals on silicite rocks in association with unidentified Mn oxides and limonite. Francevillite is orthorhombic, space group Pcan, the unit-cell parameters refined from X-ray powder diffraction data are a 10.4161(8), b 8.5078(6), c 16.7592(10) Å and V 1485.16(13) Å3. Its chemical composition (mean of 14 spot analyses) based on V+Si=2 apfu corresponds to the empirical formula (Ba0.81Ca0.11K0.10Fe0.01)Σ1.03(UO2)1.96(V1.99Si0.01)Σ2.00O8·5H2O. Raman spectrum of studied mineral corresponds to the published spectra of francevillite from Mounana mine, Gabon. Francevillite originated by the weathering of uraninium mineralization in conditions of supergene zone in-situ.
At the small historical ore deposit of Panenská Hůrka near Chrastava (northern Bohemia, Czech Republic), silver was mined in the 15th and 16th centuries. Based on our new electron microprobe investigations, its economic carrier is a mineral of the tetrahedrite group with variable As and Sb contents and with a silver content of up to 2.9 wt.%. Most of the analyses correspond to tennantite-(Zn). The most abundant sulfide at the deposit is galena, which, however, does not contain silver in levels detectable by means of an electron microprobe, nor does the other present sulfide, sphalerite. The presence of the secondary minerals cerussite and anglesite has also been confirmed.
A rare bismuth oxychloride mineral bismoclite, BiOCl, and two antimony oxide minerals senarmontite and valentinite, both ideally Sb2O3, have been found and identified in five different finds of gangue material from the Staročeské pásmo Lode of the Kutná Hora ore district (Czech Republic). The minerals were identified by electron microprobe and confirmed by Raman spectroscopy. Bismoclite was found to be closely associated with native bismuth and Sb-rich bismuthinite, also holubite, lazerckerite and terrywallaceite are present. The empirical formulas of two samples are (Bi0.87Sb0.03Fe0.04)Σ0.94O0.87(Cl0.94F0.10S0.02)Σ1.06 and Bi0.91Pb0.03Sb0.02As0.01)Σ0.97O0.91(Cl0.92F0.11S0.02)Σ1.05, respectively. The antimony oxides, senarmontite and valentinite, were found to be associated with berthierite. Senarmontite is As-rich in both samples and has the empirical formulas (Sb1.93As0.07)Σ2.00O3 and (Sb1.89As0.11)Σ2.00O, respectively. The empirical formulas of valentinite are (Sb1.95As0.03S0.02)Σ2.00O3 and (Sb1.95As0.03S0.02Fe0.01)Σ2.01O3, respectively. Two cases of intersection of the Bi-mineralization with a later Sb (and Bi-free) mineralization were encountered for the first time. In one case lazerckerite and terrywallaceite were detected in an association of a typical late Sb-mineralization with berthierite and valentinite and in the second case valentinite and berthierite were found in the Bi-mineralization with Bi- and Bi-Sb mixed members of the lillianite homologous series.
A vein hydrothermal mineralization with predominating dolomite gangue was newly found in the Plaňany I quarry (Kutná Hora Crystalline Complex, Czech Republic). The mineralization forms either a single vein reaching up to 5 cm in thick or a small stockwork hosted by migmatites, which are strongly altered and bleached to the depth up to 10 - 15 cm. Beside dolomite to Fe-rich dolomite (Dol59-81Ank18-40Ktn0-3), quartz and calcite (Cal95-99Sid0-4Rdc0-1Mgs0-1) are additional major constituents of the gangue. Minor components are chlorite of the clinochlore-chamosite series, arsenopyrite (with local admixtures of Sb, Co and Ni), pyrite (with admixtures of As), pyrrhotite and chalcopyrite. In addition, irregular domains composed of illite-muscovite, chlorite, quartz, dolomite, calcite and rutile (with admixtures of W, Nb, Cr, V and Fe) occur in vein dolomite, which likely represent partly resorbed fragments of strongly altered host rock. Various mineral thermometers indicate that the studied mineralization formed in a wide temperature range between ca. 400 and 100 °C. The overall decrease of temperature was likely finished by a temperature rejuvenation associated with formation of crystals of hexagonal pyrrhotite in drusy cavities. The presence of dolomite as a Mg-rich carbonate, very low contents of Mn and elevated contents of Cr, V, Co and Ni in hydrothermal minerals suggest a significant material contribution of basic and ultrabasic rocks, and, thus, the participation of a wide circulation of fluids in an open hydrothermal system.
Rare Mn3+ oxide, mineral bixbyite-(Mn), was found in samples from the mine dump material of the Segen Gottes Gallery, 1.6 km NW of Horní Blatná, Krušné hory Mountains, Czech Republic. Bixbyite-(Mn) occurs as steel-gray, fine-grained aggregates up to 1 cm in size with metallic lustre in quartz gangue in association of pyrolusite. Bixbyite-(Mn) is isometric, space group Ia3, the unit-cell parameter refined from X-ray powder diffraction data is a 9.4058(3) Å with V 832.12(9) Å3. The chemical composition of the studied mineral is close to the Mn end-member of the bixbyite series with Fe contents only in the range of 0 - 0.07 apfu, in addition, minor Al contents (up to 0.03 apfu) were also determined. The contents of other - elements found - Ca, Cu, Zn and Si do not exceed 0.01 apfu, in the case of P in some analyzed points 0.02 apfu. Raman spectrum of studied bixbyite-(Mn) is also given. This is the first confirmed occurrence of bixbyite-(Mn) in the Czech Republic.
New crystallographic data are provided for natrozippeite, a common supergene uranyl sulfate, for which data were previously only available for its synthetic counterpart. According to single-crystal X-ray diffraction data collected on a crystal from Widowmaker Mine (White Canyon district, San Juan County, Utah, U.S.A.) using AgKα radiation (λ = 0.56087 Å) from a microfocus X-ray anode, natrozippeite is monoclinic, P21/n, with a = 17.6620(4), b = 14.6367(3), c = 17.7042(4) Å, β = 104.433(2)°, V = 4432.3(2) Å3 (Z = 4). The structure refinement (R1 = 0.0413 for 7949 unique observed reflections with [Iobs> 3σ(I)]) confirmed that natural natrozippeite is essentially identical to the synthetic Na5(H2O)12[(UO2)8O5(SO4)4(OH)3]. A bond-valence analysis of the structure confirmed that all H2O in the natrozippeite structure is of the non-transformer type, with [4]-coordinated O atoms. This is in line with the fact that the interlayer complex contains five [6]- to [7]-coordinated monovalent cations; the bond-valence needed to be distributed throughout the structure is of low magnitude compared, e.g., to [6]- to [7]-coordinated divalent cations). The informal (so far) zippeite family, or zippeite-type structures, is further discussed with regard to the phenomena of order/disorder, polytypism, and specific discrepancies in ordering among several natural members and their synthetic counterparts.
Rare zinc hydroxyl carbonate sulfate, mineral brianyoungite, was found in the area of skarn body near the hydrothermal vein No. 13 (2nd level of the shaft Vladimír), Plavno deposit, the Jáchymov ore district, Krušné hory Mountains, Czech Republic. Brianyoungite occurs as very thin white crystalline coatings on an area of up to several cm2 on altered skarn or more rarely it forms irregular crystalline aggregates up to 2 mm in size or spherical to hemispherical aggregates composed of small thin tabular crystals. Associated minerals are gypsum, hexahydrite, hydromagnesite, nesquehonite, serpierite, smithsonite, šlikite, Zn-rich malachite and ktenasite-like mineral. Brianyoungite is probably monoclinic, the unit-cell parameters refined from X-ray powder diffraction data are: a 15.747(4), b 6.254(2), c 5.482(2) Å, β 90.63(4)°, and V 539.8(4) Å3. Its chemical analyses (mean of 4 points) correspond to the empirical formula Zn3.00 [(CO3)0.74(SO4)0.23(SiO4)0.03]Σ1.00(OH)3.95 on the basis of 3 apfu Zn. Raman and infrared spectroscopy confirm presence of (OH)-, (CO3)2- and (SO4)2- groups in its crystal structure. The origin of brianyoungite is interpreted as product of (sub)recent supergene alteration of primary sphalerite and other minerals in skarn rock in environment of abandoned mine corridors.
A preliminary EPMA-WDS study of two samples of minerals of the tetrahedrite group from the Jeleniarka (Hirschkohlung) deposit near Dobšiná revealed their surprisingly complex chemical composition. Tetrahedrite-(Fe), tetrahedrite-(Zn) as well as tetrahedrite-(Hg) were identified at the deposit. Especially interesting are high concentrations of Bi (up to 1.23 apfu, 14.75 wt. %) which were detected in tetrahedrite-(Zn) directly associated with the bismuth sulfosalts. This phase could probably represent a younger generation of minerals of the tetrahedrite group. The Bi-enriched members of the tetrahedrite group are generally very rare within all types of ore mineralization in the Western Carpathians.
Slags and fragments of metallurgical crucibles with remnants of baked batch, originating from a newly discovered locality in the Smetanova Street in the town of Jablonec nad Nisou, were studied using an electron microprobe. A rich phase composition was found. The remnants of baked batch contain metallic droplets composed of copper or Cu-Zn alloys with variable compositions, both often enclosing also inclusions of lead. These metal droplets are enclosed in a matrix formed by a Pb-rich glass, willemite, hardystonite, zincite, tenorite, cuprite and Pb-oxides. Slags have always a hemi-crystalline structure and contain silicate glass, spinelides (gahnite, franklinite, spinel, magnesioferite, cuprospinel, thermoaerogenite, magnetite), plagioclase (An68-97Ab0-25Or1-17Cu-fs0-8Slw0-1), K-feldspar (Or54-77Ab10-18An9-22 Cu-fs0-8Cn0-3Slw0-1), leucite, Ca-rich pyroxene, quartz, an unidentified Ca-Al-Fe-Mg silicate phase, zincite, tenorite, cuprite, Pb-oxides, Cu-S phases (anilite, spionkopite, geerite, digenite/roxbyite, djurleite), thiospinels (polydymite, fletcherite), sphalerite, lead, Cu-Zn alloys, copper, and remnants of (un)burnt coal. The used crucibles are common goods composed of quartzose fireclay. We suggest that the studied artifacts originated during a modern (<150 years) non-professional metallurgical activity focused largely to re-melting of metallic copper and brass. Heating of charged crucibles was realized in direct contact with burning coal. The aim of the studied metallurgical activity is not clear, it could be (i) a small hand-crafted workshop processing metal waste and producing small articles undemanding to alloy composition; (ii) an experimental hobby focused on practical learning of the metallurgical properties of the used metals, sulfides or alloys, or (iii) a crime-related activity aimed to prevent the identification of stolen artefacts made from non-ferrous metals.
