Andersonite, Andersonit or Andersonita (Na₂CaUO₂(CO₃)₃•6H₂O), or hydrated sodium calcium uranyl carbonate is a rare uranium carbonate mineral that was only described in the last half century. Named for Charles Alfred Anderson (1902-1990) of United States Geological Survey, who first described the mineral species, it is found in sandstone-hosted uranium deposits. It has a high vitreous to pearly luster and is very fluorescent. Andersonite specimens will usually glow a bright lemon yellow (or green with blue hints depending on the deposit) in ultraviolet light. The mineral is formed as a secondary mineral and as an efflorescent crust in uranium mines. It is commonly found as translucent small rhombohedral crystals that have angles close to 90 degrees although its crystal system is nominally trigonal. Its Mohs hardness is 2.5, with an average Specific Gravity of 2.9.