Uranopilite is a minor ore of uranium with the chemistry (UO2)6SO4(OH)6O2·14H2O or, hydrated uranyl sulfate hydroxide. As with many uranyl minerals, it is fluorescent and radioactive. It is straw yellow in normal light. Uranopilite fluoresces a bright green under ultraviolet light. Uranopilite contains clusters of six uranyl pentagonal bipyramids that share equatorial edges and vertices, with the clusters cross-linked to form chains by sharing vertices with sulfate tetrahedra. In uranopilite, the chains are linked directly by hydrogen bonds, as well as to interstitial H2O groups.