Small yellow/green, plate-like, crystals of metauranocircite on a dark limonitic stained Rhyolite matrix. From the Davier Mine, located in the northern Black Hills, Lawrence Co., South Dakota. Metauranocircite is a secondary uranium mineral that typically forms in the oxidized zone of some uranium deposits. As is the case with most secondary uranium minerals, the metauranocircite fluoresces bright green under UV. This specimen is radioactive, emitting approximately 400 cpm at 1 cm. The size of this small piece is 39.7 x 19.1 x 4.0 mm.