Scientific Properties: Stone Type/Family: A member of the Tourmaline family, Silicates class Category: Silicate mineral group Chemical formula: (Ca,K,Na,[])(Al,Fe,Li,Mg,Mn)3(Al,Cr, Fe,V)6 (BO3)3(Si,Al,B)6O18(OH,F)4 Crystal system: Trigonal Cleavage: Indistinct Fracture: Uneven, small conchoidal, brittle Mohs scale hardness: 7-7.5 | |