| Colemanite | |
| Category: | Inoborates |
| Formula: | Ca2B6O11·5H2O |
| Imasymbol: | Cole[1] |
| Strunz: | 6.CB.10 |
| Class: | Prismatic (2/m) (same H-M symbol) |
| Symmetry: | P21/a |
| Unit Cell: | a = 8.712(2) Å, b = 11.247(3) Å, c = 6.091(1) Å; β = 110.12°; Z = 4 |
| Color: | Colorless, white, yellowish, grey |
| Habit: | Massive granular to coarsely crystalline, most commonly nodular. |
| Cleavage: | [010] perfect, [001] distinct |
| Fracture: | Brittle uneven to subconchoidal |
| Mohs: | 4.5 |
| Luster: | Vitreous |
| Refractive: | nα = 1.586 nβ = 1.592 nγ = 1.614 |
| Opticalprop: | Biaxial (+) |
| Birefringence: | δ = 0.028 |
| Streak: | White |
| Gravity: | 2.42 |
| Fusibility: | 1.5 |
| Diagnostic: | Exfoliates on heating, produces a green flame |
| Diaphaneity: | Transparent to translucent |
| Other: | Bright pale yellow fluorescence, may phosphoresce pale green; pyroelectric and piezoelectric at very low temperature. |
| References: | [2] [3] [4] [5] |
Colemanite (Ca2B6O11·5H2O)[5] or (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.[3]
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. 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]
About 40% of the world's known colemanite reserves are at the Emet mine in western Turkey.[8] Other important sources in Turkey are found at Bigadiç and Kestelek.[9]