Vanadio-oxy-dravite
Vanadio-oxy-dravite is an IMA-recognized mineral species in the silicate class, with the chemical formula NaV₃(Al₄Mg₂)(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 3.14; Pale green streak; Vitreous luster; optically uniaxial.
IMA symbol Vodrv, IMA status: approved, named in 2012.
Found as a primary mineral in metaquartzite (granulite facies) in marble.
It is found associated with Quartz, Cr-V-bearing tremolite and mica, diopside-kosmochlor-natalyite, Cr-bearing goldmanite, escolaite-karelianite, dravite–oxy-vanadium-dravite.
As an oxy-dravite with dominant vanadium in the Y site and V3+ contents between 5 and 1.5 atoms per formula unit.