Coffinite is a uranium with formula: U(SiO4)1−x(OH)4x.
It occurs as black incrustations, dark to pale-brown in thin section. It has a grayish-black streak. It has a brittle to conchoidal fracture. The hardness of coffinite is between 5 and 6.
It was first described in 1954 for an occurrence at the La Sal No. 2 Mine, Beaver Mesa, Mesa County, Colorado and named for American geologist Reuben Clare Coffin It has widespread global occurrence in Colorado Plateau -type uranium ore deposits of uranium and vanadium and in hydrothermal vein It occurs in association with uraninite, roscoelite and amorphous