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Ca2B6O11·5H2O A colorless or white hydrated borate mineral that crystallizes in the monoclinic system and occurs in massive crystals or as nodules in clay.



(named for W. T. Coleman, 1824–93, the owner of the mine where it was discovered), a mineral of the class of borates. In terms of chemical composition it is a hydrous calcium borate, Ca[B2BO4(OH)3].H2O. Complex chains composed of B(O, OH)4 tetrahedrons and BO3 triangles bonded into a three-dimensional structure through Ca2+ ions and H2O buffer molecules are present in the crystal structure. Colemanite crystallizes in a monoclinic system, forming short, colorless crystals of columnar or dipyramidal appearance, as well as continuous fine-grained masses. Hardness on the mineralogical scale, 4–4.5; density, 2,440–2,450 kg/m3.

Colemanite is formed by precipitation, along with other borates (hydroboracite, inyoite, and borax), gypsum, and clayey deposits, from boron-containing brines of continental lakes. It is also found in the deposits of hot springs. Along with the other borates, colemanite is used as a boron ore.

References in periodicals archive ?
The other three B sources were the commercially available colemanite (Active Micronutrient Fertilisers), ulexite (ChemSupply) and di-sodium tetraborate (borax) (BDH Analar).
For the fertilisers co-granulated with colemanite, ulexite and borax, which have a basic reaction, the solution pH was between 5.
For co-granulated colemanite, the B solubility ranged from 74 to 81% of the total B content (Table 2).
The concentration of B in the leachates of co-granulated ulexite, borax and colemanite were high at the beginning (137, 189 and 89 mg B/L, respectively), and strongly decreased over time until the concentration was almost below detection limit (~10 ppb) (Fig.
This was followed by cogranulated borax (75% B leached) and co-granulated colemanite (58% B leached).
Only ~2 to 3% of added B was recovered at the end of experiment in the residual granules of co-granulated ulexite, borax and colemanite (Table 3).
In a previous study, we determined the kinetics of B release from pure ulexite, borax, colemanite and BP[O.
As a pure source, colemanite has high pH and low solubility.
Gillespie borate is comprised principally of ulexite (sodium calcium borate), with small amounts of colemanite (calcium borate) and other minerals--just like Gerstley borate.