Whewellite: Gemstones Information
Whewellite is CaC2O4H2O and forms transparent to translucent white,colourless, pale brown or pale yellow equant to short prismatic crystals of the monoclinic system with hardness 2.5–3 and SG 2.21–2.23. The RI for the alpha, beta and gamma rays is 1.489–1.491, 1.553–1.554 and 1.649–1.650, biaxial positive with birefringence 0.159–0.163. Whewellite occurs as a hydrothermal mineral in ore veins and may be found in septarian nodules. Brittleness makes faceting difficult. Large crystals are from Freital-Burgk, near Dresden Saxony, Germany, and from the Boldut mine, Kapnikbanya, Romania. The septarian nodules have been found at a site about 11 km South-east of Havre, Hill County, Montana,USA.