Sanbornite

Sanbornite is a rare barium phyllosilicate mineral with formula BaSi₂O₅. Sanbornite is a colorless to white to pale green, platey orthorhombic mineral with Mohs hardness of 5 and a specific gravity of 3.74.

Sanbornite
Sanbornite (white) with celsian (gray)—Incline, Maricopa County, California
General
Category	Phyllosilicate
Formula (repeating unit)	Ba(Si2O5)
Strunz classification	9.EF.10
Crystal system	Orthorhombic
Crystal class	Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m)
Space group	Pmcn
Unit cell	a = 4.62 Å, b = 7.68 Å c = 13.52 Å; Z = 4
Identification
Formula mass	273.50 g/mol
Color	Colorless, White
Crystal habit	Platy modulated layers
Cleavage	Perfect
Mohs scale hardness	5
Luster	Vitreous
Streak	White
Diaphaneity	Transparent to translucent
Specific gravity	3.74
Optical properties	Biaxial (-)
Refractive index	nα = 1.597, nβ = 1.616, nγ = 1.624
Birefringence	δ = 0.0270
Dispersion	Weak
References	[1][2]

It was first described from Incline, Mariposa County, California in 1932^[3] and named for mineralogist Frank B. Sanborn (1862–1936). 

This article uses material from the Wikipedia article  Metasyntactic variable, which is released under the  Creative Commons Attribution-ShareAlike 3.0 Unported License.