| Abstrakt: |
A new mineral, kasatkinite, BaCaBSiO(OH) · 6HO, has been found at the Bazhenovskoe chrysotile asbestos deposit, the Central Urals, Russia in the cavities in rhodingite as a member of two assemblages: (l) on prehnite, with pectolite, calcite, and clinochlore; and (2) on grossular, with diopside and pectolite. Kasatkinite occurs as spherulites or bunches up to 3 mm in size, occasionally combined into crusts. Its individuals are acicular to hair-like, typically split, with a polygonal cross section, up to 0.5 mm (rarely, to 6 mm) in length and to 20 μm in thickness. They consist of numerous misoriented needle-shaped subindividuals up to several dozen μm long and no more than 1 μm thick. Kasatkinite individuals are transparent and colorless; its aggregates are snow white. The luster is vitreous or silky. No cleavage was observed; the fracture is uneven or splintery for aggregates. Individuals are flexible and elastic. The Mohs' hardness is 4-4.5. D = 2.95(5), D = 2.89 g/cm. Kasatkinite is optically biaxial (+), α = 1.600(5), β = 1.603(2), γ = 1.626(2), 2 V = 30(20)°, 2 V = 40°. The IR spectrum is given. The B MAS NMR spectrum shows the presence of BO in the absence of BO groups. The chemical composition of kasatkinite (wt %; electron microprobe, HO by gas chromatography) is as follows: 0.23 NaO, 0.57 KO, 28.94 CaO, 16.79 BaO, 11.57 BO, 0.28 AlO, 31.63 SiO, 0.05 F, 9.05 HO, −0.02 −O=F; the total is 99.09. The empirical formula (calculated on the basis of O + F = 41 apfu, taking into account the TGA data) is: NaKBaCaBAlSiO(OH)F · 6.10HO. Kasatkinite is monoclinic, space group P2/ c, P2/ c, or Pc; the unit-cell dimensions are a = 5.745(3), b = 7.238(2), c = 20.79 (1) Å, β = 90.82(5)°, V = 864(1) Å, Z = 1. The strongest reflections ( d Å- I[ hkl]) in the X-ray powder diffractions pattern are: 5.89-24[012], 3.48-2.1[006], 3.36-24[114]; 3.009-100[ $$12\bar 1$$, 121, $$10\bar 6$$], 2.925-65[106, $$12\bar 2$$, 122], 2.633-33[211, 124], 2.116-29[ $$13\bar 3$$, 133, 028]. Kasatkinite is named in honor of A.V. Kasatkin (b. 1970), a Russian amateur mineralogist and mineral collector who has found this mineral. Type specimen is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow. [ABSTRACT FROM AUTHOR] |
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