Natural Crystals: Black Tourmaline (medium-large)

Tourmaline

Tourmaline is the name given to a very chemically complex (A(D₃)G₆(Si₆O₁₈)(BO₃)₃X₃Z) family of stones. With slight chemical differences it comes almost every colour varying from light to dark. All types of tourmaline form according to a hexagonal crystal system and have a hardness of 7.5 on the Mohs scales. These are considered precious stones and some varieties are highly valued.