Zeolitová mineralizace s gmelinitem-K z Jedlky u Benešova nad Ploučnicí (Česká republika)

A new locality of zeolite minerals occurs on the NE edge of the Jedlka village, at the SE slope of the Hlídka hill, 2 km to W of Benešov nad Ploučnicí (northern Bohemia, Czech Republic). The mineralization is developed in Cenozoic analcime-nepheline tephrite. Ten zeolite mineral species (gmelinite-K, analcime, harmotome, chabazite-Ca, lévyne-Ca, mezolite, natrolite, offretite, phillipsite-K, thomsonite-Ca) were found in small amygdule cavities of tephrite. The most interesting is gmelinite-K, a rare zeolite worldwide, which forms clear, white or slightly yellowish, hexagonal lenticular crystals up to 7 mm, always intergrown with the chabazite-Ca. The unit-cell parameters of gmelinite-K, refined from the powder X-ray data, are a = 13.795 (19), c = 9.811(6) Å and V = 1616.8(3) Å3; its quantitative chemical analyses correspond to the empirical formula (K2.32Ca1.86Sr0.53Na0.20Ba0.19)Σ5.10(Al8.14Si16.01O48)·22H2O.

Cu(-Ag) mineralizace z Tismic u Českého Brodu (perm blanické brázdy, Česká republika)

A mineralogical study of samples newly collected from dump material at the formerly mined locality Tismice near Český Brod (central Bohemia) revealed the presence of covellite/yarrowite, acanthite, malachite and azurite. In addition, psammitic to aleuritic detrital material originated from host Permian sandstones/arkoses is a common compound of the studied ore samples. The Cu carbonates clearly prevail among ore minerals, whereas sulphide phases are accessories. The silver-enriched covellite/yarrowite, strongly replaced by malachite and azurite, has a coarse-grained texture implying that its primary hydrothermal or late hydrothermal origin cannot be excluded. The other recorded ore minerals are clearly supergene in origin. Although the nature of the mineralization from Tismice is in general similar to other occurrences of epigenetic vein Cu mineralization hosted by the Permian sediments in the vicinity of the town of Český Brod, the enrichment in silver is reported for the first time here.

Chemická zonálnosť Ti-andraditového granátu v Ca-skarne z oblasti Magnetový vrch pri Tisovci (Slovenská republika)

Analyzed garnets from the Magnet hill area near Tisovec (Slovak Republic) are part of a Ca-skarn mineral association consisting of diopside, clinochlore and calcite. Compositionally they correspond to Ti-rich andradite (Adr50.9-73.7) with minor grossular (Grs3.8-44.5) and schorlomite (Sch0.5-41.5) components. Garnets contain up to 13 wt. % TiO2 and in all of them YFe3+>YTi ratio prevails. Both sector and oscillatory chemical zoning were observed, which is primarily caused by variable distribution of Ti contents within individual garnet crystals. The three principal zones were distinguished in BSE imaging. The brightest are Ti-enriched zones with Ti content ranging from 0.85 to 0.50 apfu. Titanium gradually decreases in transitional zone (0.17 - 0.40 apfu) and reaches the minimum values in the dark zones (0.01 - 0.13 apfu). In the Ti-enriched zones the content of Si4+ and Al3+ is decreased due to substitution of Ti4+ and Fe3+ and assumed hydrogarnet substitution (SiO4)4- ↔ (O4H4)4-.

Pb-Sb zrudnění z Antimonitové žíly, důl Rudolf, Bohutín (Česká republika)

The Pb-Sb mineralization with dominant stibnite and plagionite and associated semseyite and zinkenite was found in an archive material collected at the Antimonitová vein, Bohutín, Březové Hory ore district (Czech Republic). Plagionite forms subhedral aggregates up to 1 mm in size. The unit-cell parameters of plagionite for monoclinic space group C2/c refined from the X-ray powder data are: a 13.4890(17), b 11.8670(14), c 19.997(2) Å, β 107.199(8)° and V 3057.9(6) Å3. Its chemical composition (average of 26 analyses, based on 30 apfu) corresponds to the empirical formula Pb5.02Sb8.15S16.82. Associated zinkenite is forming subhedral crystals up to 1 mm in size. Its empirical formula can be expressed as (Cu0.25Ag0.02Fe0.01)Σ0.28Pb9.22Sb22.19S41.31 (average of 26 analyses, based on 73 apfu). Semseyite aggregates have the empirical formula (Pb8.72Fe0.14)8.86Sb8.42S20.73 (average of 11 analyses, based on 38 apfu).

Minerály kontaminovaných granitových pegmatitů z lomu Pohled u Havlíčkova Brodu (moldanubikum), část II: prvky a sulfidy

In the Pohled quarry near Havlíčkův Brod town (central part of Czech Republic), texturally and mineralogically simple contaminated anatectic pegmatites form dikes or irregular bodies cementing breccia of host metamorphic rocks (paragneisses, amphibolites) belonging to the Monotonous (Ostrong) Group of the Moldanubicum of the Bohemian Massif. They exhibit signs of intense hydrothermal overprint and also the presence of abundant disseminations, nests and veinlets of ore minerals. A detailed mineralogical study revealed the presence of an extraordinary rich ore assemblage (20 species in total, including one unnamed phase). The oldest minerals are sphalerite (rich in Fe), löllingite, Fe-Co-Ni sulphoarsenides (cobaltite, glaucodot, arsenopyrite, gersdorffite), pyrrhotite, galena and chalcopyrite, in later portion accompanied by inclusions of Bi-minerals (native bismuth, bismuthinite, joséite-A, joséite-B, ikunolite and a Pb-Bi sulphosalt). The composition of the Pb-Bi sulphosalt is equal to Ag,Fe-substituted eclarite; its identity was confirmed also by Raman spectrum. Pyrite is very abundant phase, present probably in several generations. The Fe-Co-Ni thiospinels disseminated in younger chlorite, and represented by siegenite, violarite, grimmite and an unnamed NiFe2S4 phase, are the youngest ore minerals. The mineral association as well as chemical composition of most ore minerals are well comparable to those of local polymetallic ore veins and Alpine-type veins, which give evidence for identical origin of all these ore mineralizations. The formation of pegmatite-hosted ore assemblage was long-lasting multiphase process, which took place at temperatures between ca. 350 and <120 °C during changing fugacities of sulphur, tellurium and oxygen. A distinct enrichment in cobalt and nickel of ore mineralization hosted by pegmatites (in comparison with hydrothermal veins) is explained in terms of pronounced interactions of fluids with amphibolites and serpentinites.

Atolové granáty v bazaltových metapyroklastikách z lokality Čučma - Vincent (Slovenská republika)

Atoll garnets in basalt metapyroclastics from the locality Čučma - Vincent (Slovak Republic) consist of relict cores and zonal rings. Research was focused on comparison of chemical changes in these garnet microstructures. Relict cores have composition Sps41.4-45.2Grs40.6-43.0Adr6.4-13.6 Alm1.9-6.1, inner BSE light zone in the rings has composition Grs38.2-44.9Sps39.6-43.7Alm6.3-12.4 Adr6.5-9.6 and outer BSE dark zone in the rings has composition Sps34.3-40.3Grs33.3-38.3Adr8.5-17.3 Alm12.7-17.1. The highest content of Mn2+ in the atoll garnets was observed in the relict cores (1.21 - 1.33 apfu) and subsequent decreasing trend in contents of Mn2+ from the inner parts of the rings (BSE dark zone; 1.16 - 1.29 apfu) to their edge (BSE light zone; 1.02 -1.20 apfu) is present. The opposite trend was observed for Fe2+ content. Inner parts of the garnets are replaced by actinolite and calcite with slightly higher content of Mn (Act up to 0.07 apfu; Cal up to 0.02 apfu). Matrix of basalt metapyroclastics was primarily formed by hedenbergite which was later replaced by actinolite.

Böhmit a doprovodná zeolitová mineralizace ze Soutěsek u Děčína (Česká republika)

A new locality of böhmite and zeolite minerals, called „Soutěsky above the quarry“, occurs near the quarry „Soutěsky“ on the SW slope of the Hlídka hill, eastward of the Soutěsky village, about 5 km SW od the town of Děčín (Czech Republic). The mineralization is bound to vugs of Cenozoic volcanics. Böhmite forms mostly whitish to brownish hemispherical to spherical clusters up to 5 mm in size. The unit-cell parameters of böhmite, refined from the X-ray powder data, are a 2.871 (3), b 12.216(9), c 3.699(4) Å and V 129.7(2) Å3. Chemical analyses correspond to the empirical formula (Al0.92 Si0.06)Σ0.98O(OH). The following zeolites have been found in association with böhmite: thomsonite-Ca, phillipsite-K, gismondine, chabazite-Ca and analcime, as well as calcite. Minerals crystallized in following succession: calcite I → phillipsite-K → böhmite → calcite II → thomsonite-Ca → gismondine → calcite III. Independently, (older) analcime and (younger) chabazite-Ca occur. These minerals probably crystallized from low tempered solutions, enriched in Al ions and alkalies, the source of which can be found in altered rock-forming alumosilicates (analcime, nepheline).

Pb-Bi mineralizace v amfibolitech z lomu Libodřice u Kolína (kutnohorské krystalinikum, Česká republika)

An interesting ore mineralization containing Pb-Bi minerals, present in a thin layer parallel with schistosity of the host amphibolite, was newly recognized in the Libodřice quarry near Kolín (Kutná Hora Crystalline Complex, Czech Republic). The disseminations of ore minerals are formed especially by pyrrhotite and chalcopyrite, less pyrite and accessory galena, native bismuth, cosalite, bismuthinite and joséite-B. The equilibrium textural relationships of rock-forming silicates and main sulphides indicate that the ore assemblage underwent metamorphic recrystallization together with the host rock, however, indications of younger local re-equilibrations under changed physico-chemical conditions (especially temperature, fugacity of sulphur, fugacity of oxygen) were also observed. The presence of polysynthetic lamellae in chalcopyrite suggests for its origin/re-crystallization at temperatures above 550 °C. Sporadic cosalite, stable at temperatures below 425 °C, was probably precursor of pseudomorphs today formed by galena and native bismuth. Pseudomorphs originated at temperatures below 271 °C probably due to local decrease of sulphur fugacity caused by growth of associated pyrrhotite. The local sulphurisation of small amount of native bismuth to bismuthinite and small part of pyrrhotite to pyrite finished the process of ore evolution. The presence of elevated contents of Te, Se and Ni in the studied mineralization confirms the source of these elements in the host rock environment, which was presupposed on the basis of earlier mineralogical study of Alpine-type veins in the area of the Kutná Hora Crystalline Complex.

Supergénne minerály z U-Cu rudného výskytu Východná-Nižný Chmelienec v Nízkych Tatrách (hronikum, Slovensko)

An association of supergene U-Cu and Y/REE minerals was found in a relic of old ore dump at the abandoned U deposit occurrence Východná-Nižný Chmelienec, the northern slopes of the Nízke Tatry Mts., Slovakia. They have partially recent origin, since exploration of the locality took place between 1965 and 1966. The studied mineral assem- blage is represented by goethite, malachite, uranophane and (meta)zeunerite, in a lesser extent baryte and rare zálesíite. Uranophane appears separately (globular aggregates, thin coatings) and it also forms the main part of the yellow to yellow-green crystalline crusts on the rock cracks. The chemical composition of the uranophane was determined by electron microprobe analyses and it is close to its ideal chemical formula Ca(UO2)2(SiO3OH)2·5H2O. The average chemical composition of the studied uranophane can be expressed by an empirical formula (Ca1.0Mg0.02K0.01Fe0.01Ba0.01)Σ1.05 (UO2)2.08(SiO3OH)1.84·5H2O. The infrared vibrational spectra of the studied uranophane show 3 (UO2)2+ at 850-760 cm-1; the 3 (SiO4)4- antisymmetric stretching vibration at 1000-900 cm-1; the 1 (SiO4)4- symmetric stretching vibration at 1150-1199 cm-1; the  H2O bending vibration at 1800-1600 cm-1 and OH stretching vibrations at 3407; 3408 and 3409 cm-1. The weak bands 2648; 2646 and 2651 cm-1 may be assigned to organic impurities. The calculated U-O bond length 1.83 Å corresponds to short U-O bonds in uranophane. The accessory admixtures of uranophane coatings are (meta)zeunerite and zálesíite. (Meta)zeunerite occasionally forms thin coatings of light green to emerald green tabular crystals (up tu 0.5 mm) on the surface of the rocks. Chemical analyses of (meta)zeunerite correspond to the empirical formula (Cu0.66K0.03Fe0.01Ca0.01)Σ0.71(UO2)2.11[(AsO4)1.96(PO4)0.01]Σ1.97·12H2O. Zálesíite occurs as crystalline aggregates, nests, formed by tiny acicular crystals, up to 100 µm in length. This is the second finding (occurrence) of this mineral in Slovakia. An average zálesíite chemical composition is (Ca0.83REE0.18U0.05Al0.03Ti0.01)Σ1.10(Cu5.81Fe0.06Zn0.02)Σ5.90[(AsO4)2.75 (SiO4)0.21(PO4)0.02(SO4)0.03]Σ3.01(OH)5.10·3H2O. Malachite, which has been also found in the association, is only a minor mineral in the studied locality. The formation of uranyl silicates (uranophane) and minerals of the mixite group (zálesíite), present at the studied locality, points to neutralization of acidic supergene fluids in the mine dumps. Possibly, this environment later (precipitation of baryte) passed to neutral or slightly basic conditions (precipitation of carbonates - malachite). The identified uranyl phosphates/arsenates (zeunerite/metazeunerite), typical of an acidic environment, are therefore rare.

Olivenite and cornwallite from the Podlipa copper deposit near Ľubietová, Slovakia

An interesting occurrence of olivenite and cornwallite was recently discovered in cavities of quartz at the Podlipa copper deposit near Ľubietová, Slovakia. Olivenite occurs as olive to pale green sprays or radial aggregates consisting of individual acicular crystals up to 5 mm long. Its refined unit-cell parameters (for the monoclinic space group P21/n) are: a 8.6192(13) Å, b 8.2300(11) Å, c 5.9349(8) Å, α 90.055(12)° and V 420.99(7) Å3. Studied olivenite shows intense chemical zoning caused by strong variation of As and P contents. Most of the zones are corresponding to olivenite (with P content ranging between 0.02 to 0.39 apfu), but darker zones or domains of As-rich libethenite (with As content ranging between 0.18 to 0.24 apfu) were occasionally observed. Cornwallite forms dark green massive fillings between olivenite crystals or microcrystalline botryoidal crusts. The refined unit-cell parameters (for the monoclinic space group P21/c) of botryoidal cornwallite from the Podlipa deposit are: a 4.6112(2) Å, b 5.7698(3) Å, c 17.4167(11) Å, β 92.009(5)° and V 463.10(3) Å3. The two compositional types of cornwallite were distinguished. The first type is represented by relatively homogenous aggregates with only minor contents of P (from 0.04 to 0.22 apfu). The second type occurs as polycrystalline fillings with strong chemical zoning and has much more significant variation of As and P contents, representing solid-solution series between P-rich cornwallite (with 1.41 apfu of As and 0.59 apfu of P) and As-rich pseudomalachite (with 1.37 apfu of P and 0.63 apfu of As).