Polycrase
Polycrase crystal from Rio Pomba, Minas Gerais, Brazil
General
Category	Mineral
Formula (repeating unit)	(Y,Ca,Ce,U,Th)(Ti,Nb,Ta)2O6
IMA symbol	Plc [1]
Identification
Mohs scale hardness	5-6
Specific gravity	5
Other characteristics	Radioactive

Polycrase or polycrase-(Y) is a black or brown metallic complex uranium yttrium oxide mineral with the chemical formula (Y,Ca,Ce,U,Th)(Ti,Nb,Ta)₂O₆. 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