Fluoro-richterite

Fluororichterite
Fluororichterite with calcite from Wilberforce, Monmouth Township, Haliburton County, Ontario, Canada (size: 6.6 x 4.4 x 3.8 cm)
General
Category	Silicate mineral
Formula (repeating unit)	Na(NaCa)Mg5Si8O22F2
IMA symbol	Flrct
Strunz classification	9.DE.20
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	C2/m
Unit cell	a = 9.763, b = 17.89 c = 5.122 [Å]; β = 102.25°; Z = 2
Identification
Color	Brown to brownish-red, rose-red, yellow, grey-brown, also pale to dark green
Mohs scale hardness	5–6
Luster	Vitreous
Streak	White
Specific gravity	3.17
References

Fluororichterite is a rare amphibole with formula Na(NaCa)Mg₅Si₈O₂₂F₂.

Occurrence

Fluororichterite was first reported from the Ilmen Nature Reserve, Ilmen Mountains, Chelyabinsk Oblast', Southern Urals, Russia. It was recognized by the International Mineralogical Association in 1994. Its name is derived from its fluorine content and relation to richterite.

At the type locality in the Ilmen Mountains fluororichterite occurs in carbonate veins in amphibolites and ultramafic rocks. In the Essonville occurrence in Wilberforce, Ontario it occurs in a limestone lens within a gneiss and is associated with phlogopite and calcite. It has also been reported from Austria, Germany, Italy, Spain and China. At Coyote Peak in the Coastal Range, Humboldt County, California, it occurs with a variety of rare minerals in an alkaline mafic diatreme.