Samarskite-(Y). This rare radioactive mineral is yttrium iron niobium oxide. The mineral has a superficial appearance similar to obsidian but is much heavier. Mineralogists have experienced difficulty in telling the difference between samarskite and the closely related niobium-bearing minerals aeschynite-(Y) and euxenite-(Y). All three minerals are metamict meaning that radioactive elements have deformed or destroyed the crystalline structure. This specimen was originally identified as euxenite but further work has identified species from this location as samarskite. Uranium King Claim. Big Creek Pegmatite District. Medicine Bow Mountains. Carbon Co., Wyoming.
