Common as a massive mineral in limestone (which can be formed from the chemical precipitation of calcite as well as transformation of shell, faecal and coral material) and marble (regionally or contact metamorphosed into marble). It is a late-forming replacement mineral in many environments and found in most geologic settings.
Formula: CaCo3
System: trigonal
Colour: white, yellow, red, black…
Lustre: vitreous, pearly
Hardness: 3
Streak: white
Cleavage: perfect
Fracture: conchoidal
Impurities: Mn,Fe,Zn,Co,Ba,Sr,Pb,Mg,Cu,Al,Ni,V,Cr,Mo
Uses
construction material: marble and limestone blocks in buildings and crushed to produce cement and as an aggregate
agricultural: soil treatment and a high calcium food supplement for poultry and cattle
pigment: powdered, it becomes very white (white streak) and is used in paint manufacture
pharmaceutical: for the treatment of digestive ailments
acid neutralisation: in chemistry and industry, such as mining, for water amelioration and in mine safety (sprayed on to walls in coal mining to reduce the risk of explosion from coal dust)
optical: high grade calcite was used in WWII for production of gun sights
