Calcite

Calcite, one of the most common minerals in Kansas, is the primary mineral in limestone and a main constituent of seashells. It is also often a cementing material in sandstone. Calcite has rhombic-shaped crystals, although individual crystals can rarely be seen in limestone because the calcite crystals in limestone are very small.

Generally, it is white or colorless, but it may be tinted gray, red, green, or blue. It can be scratched with a knife but not with a fingernail. The calcite crystals from the lead and zinc mines of Cherokee County are among the finest in the state. Most of those are pale yellow and some are very large.

Chemical compound: calcium carbonate
Chemical formula: CaCO₃ (Ca = calcium, C = carbon, O = oxygen)
Color: usually white or colorless, but may be tinted red, gray, blue, or green
Luster: often glassy
Hardness: 3
Specific gravity: 2.71
Amount of transparency: transparent to translucent