Colemanite

{{Short description|Borate mineral}}

{{for|the community in California formerly named Colemanite|Ryan, California}}

{{Infobox mineral

| name = Colemanite

| category = Inoborates

| image = Colemanite - USGS Mineral Specimens 096.jpg

| imagesize = 260px

| caption =

| formula = Ca₂B₆O₁₁·5H₂O

| IMAsymbol=Cole{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}

| strunz = 6.CB.10

| system = Monoclinic

| 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.

| twinning =

| 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

| pleochroism =

| streak = White

| gravity = 2.42

| density =

| melt =

| fusibility = 1.5

| diagnostic = Exfoliates on heating, produces a green flame

| solubility =

| diaphaneity = Transparent to translucent

| other = Bright pale yellow fluorescence, may phosphoresce pale green; pyroelectric and piezoelectric at very low temperature.

| references = {{cite web |first1=Stefan |last1=Schorn |display-authors=etal |title=Colemanit (Colemanite) |url=https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Colemanite |website=Mineralienatlas |year=2021}}{{cite book |last1=Klein |first1=Cornelis |last2=Hurlbut |first2=Cornelius S. Jr. |title=Manual of mineralogy: (after James D. Dana) |date=1993 |publisher=Wiley |location=New York |isbn=0-471-57452-X |edition=21st |page=422}}{{mindat |name=Colemanite |id=1108 |access-date=30 December 2021}}{{cite web |url=http://webmineral.com/data/Colemanite.shtml |website=Webmineral |title=Colemanite mineral data |access-date=30 December 2021}}{{cite web |url=http://rruff.geo.arizona.edu/doclib/hom/colemanite.pdf |website=Handbook of Mineralogy |year=2005 |title=Colemanite |first1=John W. |last1=Anthony |first2=Richard A. |last2=Bideaux |first3=Kenneth W. |last3=Bladh |first4=Monte C. |last4=Nichols}}

}}

Colemanite (Ca₂B₆O₁₁·5H₂O) 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.

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.Hildebrand, GH. (1982) Borax Pioneer: Francis Marion Smith. San Diego: Howell-North Books. p 31 {{ISBN|0-8310-7148-6}}