Sogdianite: Gemstones Information
Sogdianite is KNa(Zr,Fe3,Ti,Al)2 Li3 Si12 O30 and forms transparent to translucent violet crystals of the hexagonal system with a perfect cleavage in one direction, hardness 5–6 and SG 2.76–2.90. The RI for the ordinary and extraordinary rays is 1.606 and 1.608, uniaxial negative with birefringence 0.002. Sogdianite fluoresces dark violet under LWUV and very dark red under SW. The absorption spectrum shows an absorption area between 645 and 630 and between 493–488 nm, with additional lines at 437, 419 and 411 nm. Sogdianite occurs in a pegmatite vein with a composition near that of an alkalic granite. Locations include the Dara-i-Pioz massif, Tadzhikistan, and the Wessels mine, Kuruman, Cape Province, South Africa.