Sarcolite: Gemstone Information
Sarcolite is NaCa6Al4Si6O24F(?) and forms transparent flesh-pink to colourless equant pseudocubic hemihedral crystals of the tetragonal system with hardness 6 and SG 2.82–2.90. The RI for the ordinary and extraordinary rays is 1.604 and 1.615, uniaxial positive with birefringence 0.011. Sarcolite occurs in contact metamorphosed limestone-bearing volcanic ejecta; the only locations are Monte Somma, and Vesuvius,Campania and Anguillara, Lazio, Italy.