2 results
A new mineral, chrisstanleyite, Ag2Pd3Se4, from Hope's Nose, Torquay, Devon, England
- W. H. Paar, A. C. Roberts, A. J. Criddle, D. Topa
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- Journal:
- Mineralogical Magazine / Volume 62 / Issue 2 / April 1998
- Published online by Cambridge University Press:
- 05 July 2018, pp. 257-264
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Chrisstanleyite, Ag2Pd3Se4, is a new mineral from gold-bearing carbonate veins in Middle Devonian limestones at Hope's Nose, Torquay, Devon, England. It is associated with palladian and argentian gold, fischesserite, clausthalite, eucairite, tiemannite, umangite, a Pd arsenide-antimonide (possibly mertieite II), cerussite, calcite and bromian chlorargyrite. Also present in the assemblage is a phase similar to oosterboschite, and two unknown minerals with the compositions, PdSe2 and HgPd2Se3. Chrisstanleyite occurs as composite grains of anhedral crystals ranging from a few µm to several hundred µm in size. It is opaque, has a metallic lustre and a black streak, VHN100 ranges from 371–421, mean 395 kp/mm2 (15 indentations), roughly approximating to a Mohs hardness of 5. Dcalc = 8.308 g/cm3 for the ideal formula with Z = 2. In plane-polarised reflected light, the mineral is very slightly pleochroic from very light buff to slightly grey-green buff; is weakly bireflectant and has no internal reflections. Bireflectance is weak to moderate (higher in oil). Anisotropy is moderate and rotation tints vary from rose-brown to grey-green to pale bluish grey to dark steel-blue. Polysynthetic twinning is characteristic of the mineral. Reflectance spectra and colour values are tabulated. Very little variation was noted in eleven electron-microprobe analyses on five grains, the mean is: Ag 25.3, Cu 0.17, Pd 37.5, Se 36.4, total 99.37 wt.%. The empirical formula (on the basis of ∑M + Se = 9) is (Ag2.01Cu0.02)∑2.03 Pd3.02Se3.95, ideally Ag2Pd3Se4. Chrisstanleyite is monoclinic, a 6.350(6), b 10.387(4), c 5.683(3) Å β 114.90(5)°, space group P21/m (11) or P21(4). The five strongest X-ray powder-diffraction lines [d in Å (I)(hkl)] are: 2.742 (100) (–121), 2.688 (80) (–221), 2.367 (50) (140), 1.956 (100) (–321,150) and 1.829 (30) (–321, 042). The name is in honour of Dr Chris J. Stanley of The Natural History Museum in London. The mineral and its name have been approved by the Commission on New Minerals and Mineral Names of the International Mineralogical Association.
Bytízite, a new Cu-Sb selenide from Příbram, Czech Republic
- Pavel Škácha, Jiří Sejkora, Jakub Plášil
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- Journal:
- Mineralogical Magazine / Volume 82 / Issue 1 / February 2018
- Published online by Cambridge University Press:
- 28 February 2018, pp. 199-209
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The new mineral bytízite was found in the dump of shaft No. 16, one of the mines in the Příbram uranium and base-metal district, central Bohemia, Czech Republic. Bytízite is associated with chaméanite, příbramite, giraudite, berzelianite, umangite, eskebornite, hakite, tetrahedrite, bukovite, crookesite and uraninite in a calcite-dominant gangue. The new mineral occurs as anhedral grains up to 40 µm, growing together in aggregates up to 300 µm across. Bytízite is steel-grey in colour and has a metallic lustre. Mohs hardness is ca. 2–3; the calculated density is 6.324 g cm–3. In reflected light bytízite is grey with a yellowish hue, yellowish and brownish. Bireflectance and pleochroism are weak. Anisotropy is strong with grey to brownish rotation tints. Internal reflections were not observed. The empirical formula, based on electron-microprobe analyses, is (Cu3.00Fe0.01Ag0.01)3.02(Sb0.97As0.06)1.03Se2.94. The ideal formula is Cu3SbSe3, which requires Cu 34.71, Sb 22.16 and Se 43.13, total 100.00 wt.%. Bytízite is orthorhombic, Pnma, a = 7.9594(12), b = 10.5830(14), c = 6.8240(11) Å, with V = 574.82(15) Å3 and Z = 4. The strongest reflections of the calculated powder X-ray diffraction pattern [d, Å (I)(hkl)] are: 3.73(37)(210), 3.27(62)(211), 2.867(40)(022), 2.698(100)(122) and 2.646(37)(040). According to the single-crystal X-ray diffraction data (Robs = 0.0437), bytízite is isostructural with synthetic Cu3SbSe3. The structure of bytízite contains two Cu, one Sb, and two Se sites (the latter is occupied both by Se and S atoms). In the structure of both synthetic Cu3SbSe3 and bytízite, there are groups of three cis-edge-sharing tetrahedra [Cu3Se8], which are interlinked to a 3D framework by SbSe3 groups. Bytízite is named after its type locality, the Bytíz deposit, near the village Bytíz.