Brownish yellow crystal aggregates of the extremely rare chromium carbide mineral tongbaite from the TL in Tongbai (Liu Village, Tongbai, Nanyang, Henan Province, Peoples Republic of China). Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Tongbaite
Natural chromium carbide described in 1983 from Tongbai County, Henan.
Intro adapted from Wikipedia (CC BY-SA).
Tongbaite is an IMA-recognized mineral species in the organic mineral class, with the chemical formula Cr₃C₂.
It crystallizes in the orthorhombic crystal system (space group Pnma).
Key properties: Mohs hardness 8.5; specific gravity 6.64; Dark gray streak; Strong metallic luster; optically biaxial.
IMA symbol Tgb, IMA status: approved, named in 1982.
Found in ultramafic rocks (China).
It is found associated with Magnesiochromite, pyrrhotite, pentlandite, pyrite, chalcopyrite, cubanite, magnetite, ilmenite, altaite, violarite, awaruite, bismutohauchecornite, lead.
The name refers to Tongbai Co., China, where the mineral occurs.