Polycrase or polycrase-(Y) is a black or brown metallic complex uranium yttrium oxide mineral with the chemical formula . It is amorphous. It has a Mohs hardness of 5 to 6 and a specific gravity of 5. It is radioactive due to its uranium content (around 6%). It occurs in granitic pegmatites. Polycrase forms a continuous series with the niobium rich rare earth oxide euxenite. It was first described in 1870 at Rasvag, Hidra (Hittero) Island, near Flekkefjord, Norway. It is found in Sweden, Norway, and the United States. References Mindat with location data Webmineral Uranium minerals Thorium minerals Calcium minerals Cerium minerals Yttrium minerals Lanthanide minerals Niobium minerals Tantalum minerals Titanium minerals Oxide minerals Amorphous solids Orthorhombic minerals Minerals in space group 60 Minerals described in 1870