Whewellite is a scarce hydrous calcium oxalate mineral (CaC2O4ĚH2O). This chemical is produced biogenically, but non-biogenic whewellite has also been documented, so this natural chemical is a mineral. It has a nonmetallic luster, a clear to whitish to yellowish to brownish color, a white streak, is relatively soft (H = 2.5 to 3), is readily broken, has cleavage, and is notably lightweight for its size.
Although scarce, whewellite has been reported from geologic occurrences of widely varying origins. It is known from hydrothermal veins, uranium deposits, sedimentary concretions, geodes, and has been found associated with coal beds.
Whewellite from Germany.