Holtite: Gemstone Information

Holtite forms semitransparent light buff to cream-buff or deep olive-buff blocky orthorhombic crystals with a resinous to vitreous lustre with hardness 8.5 and SG 3.90. The RI for the alpha, beta and gamma rays is 1.705–1.746, 1.728–1.759 and 1.730–1.761, biaxial negative with birefringence 0.015. Holtite may fluoresce bright yellow in LW and dull orange in SWUV.Holtite has been found replacing a tantalite in a pegmatite at Greenbushes,Western Australia.