Lawsonite: Gemstone Information

Lawsonite is CaAl2Si2O7(OH)2H2O and forms colourless or pale blue translucent prismatic or tabular crystals of the orthorhombic system.The hardness is 7–8 and there is one direction of perfect cleavage.The SG is 3.08–3.09 and the RI for the alpha, beta and gamma rays is 1.663–1.665, 1.672–1.675, 1.682–1.686, biaxial positive, birefringence 0.019. Lawsonite occurs in low-temperature metamorphic rocks,metamorphic and glaucophane schists. The source of any fashioned lawsonite is likely to be one of the large crystals occurring at Covelo,Mendocino county, California, USA.