Colemanite
General
Category	Borate mineral
Chemical formula	CaB3O4(OH)3·H2O
Identification
Color	Colorless, white, yellowish, grey
Crystal habit	Massive granular to coarsely crystalline, most commonly nodular.
Crystal system	Monoclinic - Prismatic
Cleavage	[010] perfect, [001] distinct
Fracture	Brittle uneven to subconchoidal
Mohs Scale hardness	4.5
Luster	Vitreous
Refractive index	nα = 1.586 nβ = 1.592 nγ = 1.614
Optical Properties	Biaxial (+)
Birefringence	δ = 0.028
Streak	White
Specific gravity	2.42
Fusibility	1.5
Diagnostic Features	Exfoliates on heating, produces a green flame
Diaphaneity	Transparent to translucent
Other Characteristics	Bright pale yellow fluorescence, may phosphoresce pale green; pyroelectric and piezoelectric at very low temperature.
References	[1][2][3][4]

Colemanite (CaB₃O₄(OH)₃·H₂O) 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.^[1]

It was named after William Tell Coleman (1824-1893), owner of the mine Harmony Borax Works near Furnace Creek in Death Valley where it was first found in 1884.

See also

• List of minerals
• List of minerals named after people

References

1. ^{a b} Klein, Cornelis and Cornelius S. Hurlbut, Jr.; 1985, Manual of Mineralogy, Wiley, 20th ed., p. 347 ISBN 0-471-80580-7
2. http://www.mindat.org/min-1108.html Mindat
3. http://webmineral.com/data/Colemanite.shtml Webmineral
4. http://rruff.geo.arizona.edu/doclib/hom/colemanite.pdf Handbook of Mineralogy

• R. F. Gallup1 and L. B. Coleman (1990). "Vibrational spectra and the ferroelectric phase transition of colemanite". Physics and Chemistry of Minerals 17 (3): 271–274. doi:10.1007/BF00201460. 
• "Death Valley - Historic Resource Study - A History of Mining".

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Source: adapted by the editor from Wikipedia, the free encyclopedia; from the article "Colemanite". Image Credit.

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