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Colemanite - USGS Mineral Specimens 096.jpg
(repeating unit)
Strunz classification6.CB.10
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupP21/a
Unit cella = 8.712(2) Å,
b = 11.247(3) Å,
c = 6.091(1) Å;
β = 110.12°; Z = 4
ColorColorless, white, yellowish, grey
Crystal habitMassive granular to coarsely crystalline, most commonly nodular.
Cleavage[010] perfect, [001] distinct
FractureBrittle uneven to subconchoidal
Mohs scale hardness4.5
DiaphaneityTransparent to translucent
Specific gravity2.42
Optical propertiesBiaxial (+)
Refractive indexnα = 1.586 nβ = 1.592 nγ = 1.614
Birefringenceδ = 0.028
Diagnostic featuresExfoliates on heating, produces a green flame
Other characteristicsBright pale yellow fluorescence, may phosphoresce pale green; pyroelectric and piezoelectric at very low temperature.

Colemanite (Ca2B6O11·5H2O)[5] or (CaB3O4(OH)3·H2O)[3] is a borate mineral found in evaporite deposits of alkaline lacustrine environments. Colemanite is a secondary mineral that forms by alteration of borax and ulexite.[2]

It was first described in 1884 for an occurrence near Furnace Creek in Death Valley and was named after William Tell Coleman (1824–1893), owner of the mine "Harmony Borax Works" where it was first found.[3] At the time, Coleman had alternatively proposed the name "smithite" instead after his business associate Francis Marion Smith.[6]


Colemanite is an important ore of boron, and was the most important boron ore until the discovery of kernite in 1926. It has many industrial uses, like the manufacturing of heat resistant glass.[7]

See also[edit]


  1. ^ Mineralienatlas
  2. ^ a b Klein, Cornelis and Cornelius S. Hurlbut, Jr.; 1985, Manual of Mineralogy, Wiley, 20th ed., p. 347 ISBN 0-471-80580-7
  3. ^ a b c Mindat
  4. ^ Webmineral
  5. ^ a b Handbook of Mineralogy
  6. ^ Hildebrand, GH. (1982) Borax Pioneer: Francis Marion Smith. San Diego: Howell-North Books. p 31 ISBN 0-8310-7148-6
  7. ^ "Nitrates". Simon & Schuster's Guide to Rocks and Minerals. Simon & Schuster. 1977. p. entry 111. ISBN 978-0-671-24417-0.

External links[edit]

Spencer, Leonard James (1911). "Colemanite" . In Chisholm, Hugh (ed.). Encyclopædia Britannica. 6 (11th ed.). Cambridge University Press. p. 665.