Sulphur: Gemstones Information
Sulphur, S, forms transparent to translucent yellow crystals of the orthorhombic system which are in general too heat-sensitive to be fashioned for ornament. The crystals are dipyramidal, thick tabular and often well formed. The hardness is 1.5–2.5 and the SG 2.07. The RI for the alpha, beta and gamma rays is 1.958, 2.038 and 2.245, biaxial positive with birefringence 0.291. Sulphur is a sublimation product of volcanic fumaroles. The finest crystals are found at Cianciana, Agrigento and Racalmuto, Sicily, Italy.