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Silicate

Oxy-chromium-dravite

NaCr₃(Cr₄Mg₂)(Si₆O₁₈)(BO₃)₃(OH)₃O
Hardness7.5
Crystal systemHexagonal
ClassSilicate
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Oxy-chromium-dravite

Oxy-chromium-dravite is an IMA-recognized mineral species in the silicate class, with the chemical formula NaCr₃(Cr₄Mg₂)(Si₆O₁₈)(BO₃)₃(OH)₃O.

It crystallizes in the hexagonal crystal system (space group R3m). It is a member of the Tourmaline structural group.

Key properties: Mohs hardness 7.5; specific gravity 3.32; Green streak; Vitreous luster; optically uniaxial.

IMA symbol Ocdrv, IMA status: approved, named in 2011.

Found in Cr-V-bearing calcite-quartz-diopside metamorphic rocks (granulite facies).

It is found associated with Quartz, calcite, chromphyllite, eskolaite, chromite, uvarovite, chromian phlogopite, diopside-kosmochlor, chromian tremolite, chromian titanite.

As an oxy-dravite with dominant chromium in the Y and Z sites and magnesium the dominant divalent cation in Z.

Index entry. This entry combines official IMA/RRUFF species data with published physical-property data — a full written entry hasn’t been published yet. Browse more O minerals or help write this entry.