Coffinite

Clades: Nesosilicates
Chemical: U(SiO4)1−x(OH)4x.
Crystal system: Tetragonal.
Color: black, dark to pale-brown in thin section, with grayish-black streak.
Hardness: 5 to 6.
Region: Mesa County, Colorado.
Habitat: in sandstone and in hydrothermal vein type deposits; in association with uraninite, thorite, pyrite, marcasite, roscoelite, clays and amorphous organic matter.