Linarite: Gemstone Information
Linarite is PbCu(SO4)(OH)2 and forms elongated and characteristically tabular transparent to translucent bright to dark blue monoclinic crystals,which may be deep blue in transmitted light. There is one direction of perfect cleavage and the hardness is 2.5. The SG is 5.35 and the RI for the alpha, beta and gamma rays is 1.809, 1.838 and 1.859, biaxial negative with birefringence 0.050. Linarite is not often found in faceting quality;it occurs as an uncommon secondary mineral in the oxidized zone of lead–copper deposits. Probably the finest crystals are those found at the Mammoth mine, Tiger, Arizona, USA.