Prewittite, KPb<subscript>1.5</subscript>Cu<subscript>6</subscript>Zn(SeO<subscript>3</subscript>)<subscript>2</subscript>O<subscript>2</subscript>Cl<subscript>10</subscript>, a new mineral from Tolbachik fumaroles, Kamchatka peninsula, Russia: Description and crystal structure.
In: American Mineralogist, Jg. 98 (2013-02-01), Heft 2, S. 463-469
academicJournal
Zugriff:
Prewittite, ideally KPb1.5Cu6Zn(SeO3)2O2Cl10, was found in the fumarole field of the second cinder cone of the North Breach of the Great fissure Tolbachik eruption (1975-1976, Kamchatka peninsula, Russia). It occurs as separate olive-green tabular crystals up to 0.2 mm in maximum dimension. It has vitreous luster and brownish-green streak. Prewittite is orthorhombic, space group Pnnm, a = 9.132(2), b = 19.415(4), c = 13.213(3) Å, V = 2342.6(9) ų, Z = 4, Dcalc = 3.89 g/cm³, Dmeas = 3.90(2) g/cm³. The eight strongest lines of the powder X-ray diffraction pattern are {I [d(Å)] hkl}: 70 (8.26) 110; 60 (7.53) 101; 90 (4.111) 220, 132, 141; 100 (3.660) 212, 123; 40 (2.996) 223; 50 (2.887) 062; 40 (2.642) 322, 214; 40 (2.336) 073, 180, 244. Prewittite is biaxial (-). The optical orientation is X = a, Y = c, Z = b. The mineral has clear pleochroism: X, Y -- olive green, Z - red-brown. The mineral is very brittle with the perfect cleavage on (010) and (101). The most developed crystal forms are {010}, {001}, and {101}. The chemical composition determined by the electron-microprobe is (wt%): K2O 1.76, PbO 21.18, CuO 33.24, ZnO 8.00, SeO2 15.74, Cl 26.06, O=Cl -5.88, total 100.10. The empirical formula derived on the basis of O+Cl = 18 and sum of positive charges of cations equal to 26 is K0.53Pb1.33Cu5.87Zn1.38Se1.99O7.67Cl10.33. The crystal structure was solved by direct methods and refined to an agreement index R1 = 0.034 on the basis of 1522 independent reflections with I ≥ 2σI. It is based upon metal oxide selenite chloride layers parallel to (010) and linked through K-Cl and Pb-Cl bonds to the K and Pb atoms located in the interlayer. The mineral name honors Charles T. Prewitt (b. 1933) in recognition of his important contributions to crystal chemistry of minerals and planetary materials. [ABSTRACT FROM AUTHOR]
Titel: |
Prewittite, KPb<subscript>1.5</subscript>Cu<subscript>6</subscript>Zn(SeO<subscript>3</subscript>)<subscript>2</subscript>O<subscript>2</subscript>Cl<subscript>10</subscript>, a new mineral from Tolbachik fumaroles, Kamchatka peninsula, Russia: Description and crystal structure.
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Autor/in / Beteiligte Person: | SHUVALOV, ROBERT R. ; VERGASOVA, LIDIYA P. ; SEMENOVA, TATYANA F. ; FILATOV, STANISLAV K. ; KRIVOVICHEV, SERGEY V. ; SIIDRA, OLEG I. ; RUDASHEVSKY, NIKOLAY S. |
Zeitschrift: | American Mineralogist, Jg. 98 (2013-02-01), Heft 2, S. 463-469 |
Veröffentlichung: | 2013 |
Medientyp: | academicJournal |
ISSN: | 0003-004X (print) |
DOI: | 10.2138/am.2013.4174 |
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