Spurrite: Gemstones Information
Spurrite is Ca5(SiO4)2(CO3); the monoclinic, pseudo-orthorhombic crystals are anhedral but massive opaque to translucent lavender-grey to purple masses have been used ornamentally. They show one direction of perfect cleavage; the hardness is 5 and the SG 3.02. The RI for the alpha, beta and gamma rays is 1.637–1.641, 1.672–1.676, 1.676–1.681,biaxial negative with birefringence 0.039. Spurrite occurs as a product of high-temperature thermal metamorphism along the contact between carbonate rock and mafic magma. Most ornamental spurrite has come from Mexico, probably from the Santa Juana mine, Velardena, Durango or from the Encantada district, Coahuila.