1) Ore 1) Uranium mineral 
Coffinite is a uranium-bearing silicate mineral 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...
(from the article `mineral deposit`) ...ions are stable and uranium can be transported by groundwater; however, when uranyl ions encounter a reducing agent such as organic matter, U4+ ...
a mineral, black uranous silicate, USiO, an important ore of uranium.