Tongbaite

Tongbaite is a rare mineral that has the chemical formula Cr₃C₂, or chromium carbide.

Tongbaite
General
Category	Carbide mineral
Formula (repeating unit)	Cr3C2
Strunz classification	1.BA.15
Crystal system	Orthorhombic
Crystal class	Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m)
Space group	Pnma
Unit cell	a = 5.52 Å, b = 11.48 Å c = 2.82 Å; Z = 4
Identification
Color	Pale brownish yellow; pale violet in reflected light
Crystal habit	Prismatic crystals, pseudohexagonal
Tenacity	Brittle
Mohs scale hardness	9.6
Luster	Metallic
Diaphaneity	Opaque
Specific gravity	6.64 calculated
References	[1][2][3]

It was first described in 1983 for an occurrence in Liu village, Tongbai County (桐柏县), Henan Province, China and named for the locality.^[2] It occurs in an ultramafic rock deposit.^[1] It has also been reported from the Tibet Autonomous Region and from the Isovsky District in the Urals of Russia. 

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