Black sharp crystal of the very rare member of the tourmaline group feruvite from the type locality in New Zealand (Repanga Island (Cuvier Island),, Thames-Coromandel District, Waikato Region, New Zealand). Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Feruvite
A calcium-iron tourmaline — the iron-rich, near-black member of the tourmaline group.
Intro adapted from Wikipedia (CC BY-SA).
Feruvite is an IMA-recognized mineral species in the silicate class, with the chemical formula CaFe²⁺₃(Al₅Mg)(Si₆O₁₈)(BO₃)₃(OH)₃(OH).
It crystallizes in the hexagonal crystal system (space group R3m). It is a member of the Tourmaline structural group.
Key properties: Mohs hardness 7; specific gravity 3.207; Gray streak; Vitreous to dull luster; optically uniaxial.
IMA symbol Fuvt, IMA status: approved, named in 1987.
By hydrothermal replacement of silicates in a pegmatitic rock.
It is found associated with Dravite, quartz, microcline, chlorapatite, pyrite.
The name refers to iron (FERrum), in the formula and the similarity to uvite.