Vanadio-oxy-chromium-dravite, NaV3(Cr4Mg2)(Si6O18)(BO3)3(OH)3O, a new mineral species of the tourmaline supergroup
2014; Mineralogical Society of America; Volume: 99; Issue: 5-6 Linguagem: Inglês
10.2138/am.2014.4568
ISSN1945-3027
AutoresFerdinando Bosi, Л. З. Резницкий, Henrik Skogby, Ulf Hålenius,
Tópico(s)Mineralogy and Gemology Studies
ResumoVanadio-oxy-chromium-dravite, NaV3(Cr4Mg2)(Si6O18)(BO3)3(OH)3O, is a new mineral of the tourmaline supergroup. It is found in metaquartzites of the Pereval marble quarry (Sludyanka, Lake Baikal, Russia) in association with quartz, Cr-V-bearing tremolite and muscovite-celadonitechromphyllite- roscoelite, diopside-kosmochlor-natalyite, Cr-bearing goldmanite, escolaite-karelianite, dravite-oxy-vanadium-dravite, V-bearing titanite and rutile, ilmenite, oxyvanite-berdesinskiite, shreyerite, plagioclase, scapolite, zircon, pyrite, and an unnamed oxide of V, Cr, Ti, U, and Nb. Crystals are emerald green, transparent with a vitreous luster, pale green streak, and conchoidal fracture. Vanadio-oxy-chromium-dravite has a Mohs hardness of approximately 7½, and a calculated density of 3.3 g/cm3. In plane-polarized light, vanadio-oxy-chromium-dravite is pleochroic (O = dark green, E = pale green) and uniaxial negative: ω = 1.767(5), ε = 1.710(5). Vanadio-oxy-chromium-dravite is rhombohedral, space group R3m, with the unit-cell parameters a = 16.1260(2), c = 7.3759(1) Å, V = 1661.11(4) Å3, Z = 3. Crystal chemistry analysis resulted in the empirical structural formula:
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