Calcite

From: Madagascar

Hardness: 3 on the mohr's scale

Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate. Calcite is a common constituent of sedimentary rocks, limestone in particular, much of which is formed from the shells of dead marine organisms. Approximately 10% of sedimentary rock is limestone.Calcite is the primary mineral in metamorphic marble. It also occurs as a vein mineral in deposits from hot springs, and it occurs in caverns as stalactites and stalagmites