Ettringite: Gemstone Information
Euxenite–(Y) is (Y,Ca,Ce,U,Th)(Nb,Ta,Ti)2O6 and occasionally provides opaque greenish black, brownish black or black cabochon material.Euxenite is a member of the orthorhombic system and is typically metamict with hardness 5.5–6.5 and SG 5.16. Material may be radioactive. The RI range 2.06–2.24 is beyond the refractometer limit. Euxenite-(Y) occurs in granite pegmatites or as detrital grains. Locations are widespread; large crystals have been reported from Vohimasina and other sites in Madagascar.