Mineral Information and Data:

CaC2O4 • H2O [CNMNC approved formula]

Named in 1852 for William Whewell (1794-1866), English naturalist and scientist, professor of moral philosophy, professor of mineralogy at Cambridge, inventor of the system of crystallographic indexing.

IMA status : Approved Species 1967 ()
(8th edition) :  
  (50) Salts of Organic Acids and Hydrocarbons
  (50.01) (Oxalates)
(10th edition) :
  (10) Organic Compounds
  (10.A) Salts of Organic Acids
  (10.AB) Oxalates
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Unit cell: a = 6.276, b = 14.561, c = 10.012, β = 107.083°
Crystal Habit: Crystals equant or short prismatic, tabular, twinning common, massive, coarsely crystalline
Twinning: Very common on {101} as twin and contact plane, with or without re-entrants
Color: Colorless, white, yellowish or brownish
Diaphaneity: Transparent to translucent
Luster: Vitreous to pearly
Hardness (Mohs): 2.5-3
Measured Density: 2.21 to 2.23 g/cm3
Cleavage: 4; {101} good, {001} and {010} distinct, {110} indistinct
Tenacity: Brittle
Fracture: Conchoidal
Streak: White
Geologic Setting: Of uncommon occurrence as a low-temperature primary hydrothermal mineral in carbonate-sulfide veins, geodes, or septarian nodules; may be associated with coal measures or formed by oxidation of organic material in surrounding rocks; in some uranium deposits.
Mineral Association: Calcite, barite, sphalerite, pyrite, weddellite, waxy hydrocarbons
Luminescent Properties: Fluorescent.
Other Properties: Gemstone Extremely Rare. BioMineral.


Colorless twinned whewellite crystal on calcite
Origin: Burgk, Dresden, Saxony, Germany
Picture size: 7 mm (top), 5 mm (bottom)
Photo and Owner: Thomas Witzke


Whewellite with quartz
Origin: Dalnegorsk, Russia
Sample size: 11 x 7 x 6 cm
Photo: Rob Lavinsky


(zoom-in of above)


Origin: near Elm Springs, Meade Co., South Dakota, USA
Sample size: 5.5 x 3 x 3 cm
Photo: Tom Loomis