Wiluite Locality: Wilui River, Yakutxk, Siberia, Russia Size: small cabinet, 6.9 x 4.0 x 2.7 cm Wiluite If the name of this species is unfamiliar to you, it is a rare member of the vesuvianite family of minerals. This matrix specimen displays a clearly tetragonal habit. It is a doubly terminated, lustrous, black wiluite crystal, measuring 2.5 cm in length. Sharp. Ex. Richard Hauck Collection. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Wiluite
A dark-green boron-bearing vesuvianite relative from Yakutia's Vilyuy River.
Intro adapted from Wikipedia (CC BY-SA).
Wiluite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₁₉(Al,Mg)₁₃(B, ,Al)₅(SiO₄)₁₀(Si₂O₇)₄(O,OH)₁₀.
It crystallizes in the tetragonal crystal system (space group P4/nnc). It is a member of the Vesuvianite structural group.
Key properties: Mohs hardness 6; specific gravity 3.36; Colorless streak; Vitreous luster; refractive index 1.723; optically uniaxial.
IMA symbol Wil, IMA status: approved, named in 1997.
Found in metasomatized skarn (Russia). In fragments of metasomatized carbonate-rich xenoliths in volcanic ejecta (Italy).
It is found associated with Grossular, serpentine minerals, carbonate, limonitized pyrite, chlorite, ‘achtarandite’.
The name refers to the Wilui River, Russia.