A mineral (belonging to the orthorhombic crystal system but usually metamict) that consists of an oxide of titanium, niobium, tantalum, uranium, yttrium, and other elements, and occurs as short, prismatic, black crystals.
In 1988 (Mineral. Mag. 52 292/2) the official name was altered to "polycrase-(Y)".
Mid 19th century; earliest use found in American Journal of Science. From German Polykras from ancient Greek πολυ- + κρᾶσις mixture, so called on account of its many constituents.