Definition of colemanite in US English:



  • A white crystalline mineral, typically occurring as glassy prisms, consisting of hydrated calcium borate.

    • ‘Between 1921 and 1925 he began to develop new colemanite holdings in Clark County, Nevada.’
    • ‘Boron never occurs as a free element, but always as a compound in minerals such as borax (sodium borate; Na 2 B 4 O 7), colemanite (calcium borate; Ca 2 B 6 O 11), and ulexite (sodium calcium borate; NaCaB 5 O 9).’
    • ‘The alternative, calcium hexaborate pentahydrate, is called colemanite and is much less soluble than ulexite.’
    • ‘I have seen realgar inclusions in colemanite turn yellow in a few months (no oxidation possible).’
    • ‘He recognized that quick exploitation of the rich, extensive, easily accessible colemanite in the Calico mine was the key to consolidating his position as the industry's foremost producer.’


Named after William T. Coleman(1824–93) + -ite.