The Mineral colemanite
Colemanite forms in evaporite deposits together with other borates, and is one of the more stable of borate minerals. It is pyroelectric, and develops an electrical charge during a change of temperature. The crystal symmetry of prismatic monoclinic minerals would scientifically disqualify them from being pyroelectric, since pyroelectricity is directly related to crystal symmetry. This mineral is therefore regarded as a scientific oddity, as no satisfactory explanation has been given to how Colemanite is pyroelectric.
Colemanite was named after William T. Coleman, a mine owner who lived in San Francisco.
Colorless to white, yellow, brown
Colemanite has many important uses. It is a significant ore of boron, and was the most important ore prior to the discovery of Kernite in 1926. It is also used in the manufacture of heat resistant glass, and has other industrial, medicinal, and cosmetic uses. It is a popular collector mineral.
Some of the largest deposits of Colemanite are in the the Southwestern U.S. Very large crystals come from Death Valley, Inyo Co., California. Crystal-filled nodules associated with Celestine were found in the Calico district in San Bernardino Co., California. Other California Colemanite deposits are Boron, in the Kramer District, Kern Co.; Tick Canyon, Lang, Los Angeles Co; and the Boraxo Mine, Inyo Co. In Nevada, it comes from the Muddy Mountains, Clark Co.
Colemanite localities outside the U.S. include Bigadic, Marmara Region, Turkey; the dry lake deposits in the Atacama Desert of Chile; Salinas Grandes, Argentina; and the Indebor Deposit, Kazakhstan.
Common Mineral Associations
Ulexite, Borax, Realgar, Celestine
Distingushing Similar Minerals
Celestine - Lower hardness, higher specific gravity.
Calcite - Lower hardness, has perfect rhombohedral cleavage.
- Different mode of occurrence.