Polycrase or polycrase- is a black or brown metallic complex uranium

Uranium

Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...

 yttrium

Yttrium

Yttrium is a chemical element with symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and it has often been classified as a "rare earth element". Yttrium is almost always found combined with the lanthanides in rare earth minerals and is...

 oxide mineral

Oxide mineral

The oxide mineral class includes those minerals in which the oxide anion is bonded to one or more metal ions. The hydroxide bearing minerals are typically included in the oxide class...

 with 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

Specific gravity

Specific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...

 of 5. It is radioactive due to its uranium content (around 6%). It occurs in granitic

Granite

Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...

 pegmatite

Pegmatite

A pegmatite is a very crystalline, intrusive igneous rock composed of interlocking crystals usually larger than 2.5 cm in size; such rocks are referred to as pegmatitic....

s.

It was first described in 1870 at Rasvag

Rasvåg

Rasvåg is one of the two harbours on the Norwegian island Hidra. The island is located in Flekkefjord municipality.-See also:*Kirkehamn...

, Hidra (Hittero) Island, near Flekkefjord

Flekkefjord

is a town and municipality in the county of Vest-Agder, Norway.The town of Flekkefjord was established as a municipality on 1 January 1838 . The rural municipalities of Bakke, Gyland, Hidra, and Nes were merged with Flekkefjord on 1 January 1965.Flekkefjord is the westernmost town of the...

, Norway

Norway

Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

. It is found in Sweden

Sweden

Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

, Norway, and the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

.