Colemanite (Ca2B6O11·5H2O) or (CaB3O4(OH)3·H2O) is a
borate mineral
The borate minerals are minerals which contain a borate anion group. The borate (BO3) units may be polymerised similar to the SiO4 unit of the silicate mineral class. This results in B2O5, B3O6, B2O4 anions as well as more complex structures whi ...
found in
evaporite
An evaporite () is a water-soluble sedimentary mineral deposit that results from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporite deposits: marine, which can also be described as ocean ...
deposits
A deposit account is a bank account maintained by a financial institution in which a customer can deposit and withdraw money. Deposit accounts can be savings accounts, current accounts or any of several other types of accounts explained below. ...
of alkaline
lacustrine
A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much larger ...
environments. Colemanite is a secondary mineral that forms by alteration of
borax
Borax is a salt (ionic compound), a hydrated borate of sodium, with chemical formula often written . It is a colorless crystalline solid, that dissolves in water to make a basic solution. It is commonly available in powder or granular form ...
and
ulexite
Ulexite (NaCaB5O6(OH)6·5H2O, hydrated sodium calcium borate hydroxide), sometimes known as TV rock or Television stone, is a mineral occurring in silky white rounded crystalline masses or in parallel fibers. The natural fibers of ulexite conduc ...
.
It was first described in 1884 for an occurrence near Furnace Creek in
Death Valley
Death Valley is a desert valley in Eastern California, in the northern Mojave Desert, bordering the Great Basin Desert. During summer, it is the hottest place on Earth.
Death Valley's Badwater Basin is the point of lowest elevation in Nort ...
and was named after
William Tell Coleman
William Tell Coleman (1824–1893) was an American pioneer in the settlement of California.
Early life
William Tell Coleman was born in Cynthiana in Harrison County, Kentucky on February 29, 1824. He was educated at St. Louis University in Misso ...
(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
Francis Marion Smith (February 2, 1846 – August 27, 1931) (once known nationally and internationally as "Borax Smith" and "The Borax King" ) was an American miner, business magnate and civic builder in the Mojave Desert, the San Francisco ...
.
Uses
Colemanite is an important
ore
Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 April ...
of
boron
Boron is a chemical element with the symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the ''boron group'' it has th ...
, and was the most important boron ore until the discovery of
kernite
Kernite, also known as rasorite, is a hydrated sodium borate hydroxide mineral with formula . It is a colorless to white mineral crystallizing in the monoclinic crystal system typically occurring as prismatic to acicular crystals or granular mass ...
in 1926. It has many industrial uses, like the manufacturing of heat resistant glass.