Colemanite

Colemanite
General
CategoryInoborates
Formula
(repeating unit)
Ca2B6O11·5H2O
IMA symbolCole[1]
Strunz classification6.CB.10
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupP21/a
Unit cella = 8.712(2) Å,
b = 11.247(3) Å,
c = 6.091(1) Å;
β = 110.12°; Z = 4
Identification
ColorColorless, white, yellowish, grey
Crystal habitMassive granular to coarsely crystalline, most commonly nodular.
Cleavage[010] perfect, [001] distinct
FractureBrittle uneven to subconchoidal
Mohs scale hardness4.5
LusterVitreous
StreakWhite
DiaphaneityTransparent to translucent
Specific gravity2.42
Optical propertiesBiaxial (+)
Refractive indexnα = 1.586 nβ = 1.592 nγ = 1.614
Birefringenceδ = 0.028
Fusibility1.5
Diagnostic featuresExfoliates on heating, produces a green flame
Other characteristicsBright pale yellow fluorescence, may phosphoresce pale green; pyroelectric and piezoelectric at very low temperature.
References[2][3][4][5][6]

Colemanite (Ca2B6O11·5H2O)[6] or (CaB3O4(OH)3·H2O)[4] 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.[3]

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.[4] At the time, Coleman had alternatively proposed the name "smithite" instead after his business associate Francis Marion Smith.[7]

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Schorn, Stefan; et al. (2021). "Colemanit (Colemanite)". Mineralienatlas.
  3. ^ a b Klein, Cornelis; Hurlbut, Cornelius S. Jr. (1993). Manual of mineralogy: (after James D. Dana) (21st ed.). New York: Wiley. p. 422. ISBN 0-471-57452-X.
  4. ^ a b c Colemanite, Mindat.org, retrieved 30 December 2021
  5. ^ "Colemanite mineral data". Webmineral. Retrieved 30 December 2021.
  6. ^ a b Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. (2005). "Colemanite" (PDF). Handbook of Mineralogy.
  7. ^ Hildebrand, GH. (1982) Borax Pioneer: Francis Marion Smith. San Diego: Howell-North Books. p 31 ISBN 0-8310-7148-6