Schoepite

Schoepite, empirical formula (UO₂)₈O₂(OH)₁₂•12(H₂O) is a rare alteration product of uraninite in hydrothermal uranium deposits. It may also form directly from ianthinite. The mineral presents as a transparent to translucent yellow, lemon yellow, brownish yellow, or amber orthorhombic tabular crystals. Although over 20 other crystal forms have been noted; rarely in microcrystalline aggregates. When exposed to air schoepite converts over a short time to the metaschoepite form (UO₃ • nH₂O, n < 2) within a few months of being exposed to ambient air.