Colemanite

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

Colemanite (Ca₂B₆O₁₁·5H₂O)^[6] or (CaB₃O₄(OH)₃·H₂O)^[4] 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.^[3]

Colemanite
General
Category	Inoborates
Formula	Ca2B6O11·5H2O
IMA symbol	Cole[1]
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	[2][3][4][5][6]

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.^[4] At the time, Coleman had alternatively proposed the name "smithite" instead after his business associate Francis Marion Smith.^[7]

Uses

Colemanite was the most important ore of boron until the discovery of kernite in 1926. It has many industrial uses such as in heat resistant glass manufacturing.^[8]

Occurrence

About 40% of the world's known colemanite reserves are at the Emet mine in western Turkey.^[9] Other important sources in Turkey are found at Bigadiç and Kestelek.^[10]

See also

• List of minerals
• List of minerals named after people