Colemanite Value, Price, and Jewelry Information


COLEMANITE: Boron, California (26.50). Photo © Joel E. Arem, PhD, FGA. Used with permission.

Colemanite is cut only as a curiosity, since it has no attractive colors. Faceted gems are normally colorless, have a low dispersion (no fire) and are brittle and fragile as well as difficult to cut. They have no appeal except to collectors of the unusual, and material for cutting is potentially abundantly available, since transparent material is not extremely rare.

Colemanite Value

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Colemanite Information

DataValue
NameColemanite
Crystallography Monoclinic. Crystals are equant, prismatic, pseudorhombohedral; massive, cleavable; granular, and as aggregates.
Colors Colorless, white, grayish, yellowish white.
Luster Vitreous to adamantine.
Fracture Subconchoidal to uneven. Brittle.
Hardness 4.5
Specific Gravity 2.42
Birefringence 0.028
Cleavage Perfect 1 direction.
Stone SizesCould be as much as 50-100 carats from large crystals or masses. Crystals are normally up to about 1 inch in size. Smithsonian Institution (Washington, D.C): 14.9 (California).
Luminescence May fluoresce and phosphoresce strong yellowish white or greenish white in SW.
Spectral Not diagnostic
FormulaCa2B6O11 · 5H2O.
Pleochroism None

Optics: a = 1.586; β = 1.592; γ= 1.614.

Biaxial (+), 2V  ~55°.

Occurrence: In saline lake deposits in arid regions.

Widespread at localities in California, especially Boron and Death Valley.

Argentina; USSR; Turkey.

Comments: Colemanite is cut only as a curiosity, since it has no attractive colors. Faceted gems are normally colorless, have a low dispersion (no fire) and are brittle and fragile as well as difficult to cut. They have no appeal except to collectors of the unusual, and material for cutting is potentially abundantly available, since transparent material is not extremely rare.

Name: After William T. Coleman, owner of the mine where the mineral was first found