Clinohumite: Gemstones Information
Transparent gem-quality bright yellow to deep orange clinohumite, a monoclinic member of the humite group of silicates with the composition ((Mg,Fe2)9(SiO4)4(F,OH))2 was found in recent years in the Pamirs of Tadzhikistan. The hardness is 6, the SG about 3.18 and the RI 1.623–1.702, 1.636–1.709 and 1.651–1.728 with a birefringence of 0.024–0.036; biaxial positive. A yellow fluorescence may be seen under SWUV. The occurrence is in contact zones in limestone or dolomite.A dark brown variety has been found in the Taymyr region,Siberia. The RI is in the range 1.640–1.671 with birefringence 0.039 and SG 3.35.