Thorite: Gemstones Information
Thorite is (Th,U)SiO4 forms nearly opaque yellow-orange or brown square prisms or pseudo-octahedral crystals of the tetragonal system though the mineral is commonly metamict and measurably radioactive.The hardness is 4.5–5 and the SG 4.0–6.7. The RI for the ordinary and extraordinary rays is 1.78–1.82, uniaxial positive. Thorite occurs as an accessory mineral in felsic igneous rocks and their associated pegmatites. Some gem material is reported from the Mogok area of Myanmar.