Serandite: Gemstones Information
Sérandite is Na(Mn2,Ca)2Si3O8(OH) forming a series with pectolite and exceptionally beautiful faceted specimens have been obtained from transparent rose-red, orange or salmon-pink elongated prismatic crystals of the triclinic system. There are two directions of perfect cleavage; the hardness and SG are 5–5.5 and 3.42. The RI for the alpha, beta and gamma rays is 1.668, 1.671 and 1.703 biaxial positive with birefringence 0.028. Sérandite occurs in pegmatites cutting syenites and nepheline syenites in an intrusive alkalic gabbro-syenite complex at Mt Saint Hilaire, Quebec, Canada.