Colemanite

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]

For the community in California formerly named Colemanite, see Ryan, California.

Colemanite
General
Category	Inoborates
Formula (repeating unit)	Ca2B6O11·5H2O
Strunz classification	6.CB.10
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P21/a
Unit cell	a = 8.712(2) Å, b = 11.247(3) Å, c = 6.091(1) Å; β = 110.12°; Z = 4
Identification
Color	Colorless, white, yellowish, grey
Crystal habit	Massive granular to coarsely crystalline, most commonly nodular.
Cleavage	[010] perfect, [001] distinct
Fracture	Brittle uneven to subconchoidal
Mohs scale hardness	4.5
Luster	Vitreous
Streak	White
Diaphaneity	Transparent to translucent
Specific gravity	2.42
Optical properties	Biaxial (+)
Refractive index	nα = 1.586 nβ = 1.592 nγ = 1.614
Birefringence	δ = 0.028
Fusibility	1.5
Diagnostic features	Exfoliates on heating, produces a green flame
Other characteristics	Bright pale yellow fluorescence, may phosphoresce pale green; pyroelectric and piezoelectric at very low temperature.
References	[1][2][3][4][5]

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]

Uses

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

• List of minerals
• List of minerals named after people

References

1. Mineralienatlas
2. Klein, Cornelis and Cornelius S. Hurlbut, Jr.; 1985, Manual of Mineralogy, Wiley, 20th ed., p. 347 ISBN 0-471-80580-7
3. Mindat
4. Webmineral
5. 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.

• 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. Bibcode:1990PCM....17..271G. doi:10.1007/BF00201460.
• "Death Valley - Historic Resource Study - A History of Mining".

External links

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