This is the blue apatite crystal in calcite. Dimensions: 1.7 x 1.3 x 1.1″ (4.3 x 3.3 x 2.7cm). Weight – 1.1oz (31 grams). Origin: Russia, Siberia.
Some information about apatite:
Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite and chlorapatite, named for high concentrations of OH, F and Cl ions, respectively, in the crystal. The formula of the admixture of the four most common endmembers is written as Ca10(PO4)6(OH,F,Cl)2, and the crystal unit cell formula of the individual minerals are written as Ca10(PO4)6(OH)2, Ca10(PO4)6(F)2 and Ca10(PO4)6(Cl)2.
Apatite is one of a few minerals produced and used by biological micro-environmental systems. Apatite is the defining mineral for 5 on the Mohs scale. Hydroxyapatite, also known as hydroxylapatite, is the major component of tooth enamel and bone mineral. A relatively rare form of apatite in which most of the OH groups are absent and containing many carbonate and acid phosphate substitutions is a large component of bone material.
The primary use of apatite is in the manufacture of fertilizer. Used as a gemstone. Green and blue varieties in finely divided form, are pigments with excellent covering power.