Whewellite is a rare calcium oxalate mineral known from low temperature primary hydrothermal carbonate-sulphide veins, coal measures deposits and some uranium deposits. This staggeringly large and immaculately formed monoclinic Whewellite crystal comes from the latter class, at Ronneburg U deposit near Gera, Thuringia in Germany. This is probably the Lichtenberg opencast site at Ronneburg that was closed in 1990 and subsequently backfilled and restored. Fine Whewellite crystals are extremely rare and this is an exceptional example, reaching over 3.6 cm in length. There are a few 'nibbles' along the two edges of the termination, but Whewellite is a soft mineral and for perfection in crystal form for the species this is a remarkable specimen.