Gaylussite: Gemstone Information
Colourless transparent gaylussite, Na2Ca(CO3)25H2O occurs as flattened wedge-shaped crystals of the monoclinic system with a hardness of 2.5–3 and one direction of perfect cleavage. The SG is near 1.99 and the RI for the alpha, beta and gamma rays is 1.44, 1.516 and 1.523, biaxial negative, birefringence 0.077. Gaylussite occurs in evaporates or shales from alkali lakes,notably Searles Lake, San Bernardino County, California, USA. The mineral does not make an ideal gemstone since surfaces may well develop a white appearance as the crystals dry out after recovery. Dehydration rules out ornamental use as specimens need to be kept in sealed containers.