Outstanding orange brown crystals of the extremely rare rare-earth borofluorosilicate mineral okanoganite-(Y) from the type locality: Washington Pass, Okanogan County, Washington, United States of America. Ex Vandenbroucke Museum collection specimen, from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Okanoganite-(Y)
Okanoganite-(Y) is an IMA-recognized mineral species in the silicate class, with the chemical formula (Y,REE,Ca,Na,Th)₁₆(Fe³⁺,Ti)(Si,B,P)₁₀(O,OH)₃₈F₁₀.
It crystallizes in the hexagonal crystal system (space group R3m). It is a member of the Okanoganite structural group.
Key properties: Mohs hardness 4; specific gravity 4.35; White streak; optically uniaxial.
IMA symbol Oka-Y, IMA status: approved, named in 1979.
Found in miarolitic cavities in a peralkalic arfvedsonite-bearing granite.
It is found associated with Quartz, microcline, zircon, arfvedsonite, bastnäsite, zektzerite, astrophyllite.
The name refers to Okanogan Co., Washington, USA, and the yttrium content.