Dolomite

Dolomite – CaMg(CO3)2
Class: Carbonates
Crystal System: Hexagonal
Hardness: 3.5-4
Fluorite
Talc (1)Diamond (10)
Softer than glass. A steel knife scratches it.
Origin: Brumado, Bahia – Brazil
Did you know?

Dolomite builds entire mountain ranges, including the Italian range named after it, yet almost never forms in today's seas and resists easy growth in the lab. Geologists still call this the dolomite problem.