Colemanite Value, Price, and Jewelry Information

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Colorless, round brilliant colemanite, 0.39 cts, 5 mm, Billie Mine, Boron, California. © The Gem Trader. Used with permission.

Colemanite is an abundant mineral, and transparent material isn’t rare. However, gem cutters rarely facet these typically pale stones. Difficult to cut and wear, colemanites are better suited for collectors of unusual gemstones.

Colemanite Information

Data Value
Name Colemanite
Crystallography Monoclinic. Crystals are equant, prismatic, pseudorhombohedral; massive, cleavable; granular, and as aggregates.
Refractive Index 1.586-1.614
Colors Colorless, white, grayish, yellowish white, light amber-orange, brown.
Luster Vitreous to adamantine
Hardness 4.5
Fracture Subconchoidal to uneven
Specific Gravity 2.42
Birefringence 0.028
Cleavage Perfect 1 direction
Dispersion Weak
Heat Sensitivity Very heat sensitive
Luminescence May fluoresce and phosphoresce strong yellowish white or greenish white.
Luminescence Present Yes
Luminescence Type Fluorescent, Phosphorescent
Transparency Translucent to transparent
Absorption Spectrum Not diagnostic
Formula Ca2B6O11 · 5H2O
Pleochroism None
Optics a = 1.586; β = 1.592; γ = 1.614. Biaxial (+), 2V  ~ 55°.
Optic Sign Biaxial +
Etymology After William T. Coleman, owner of the mine where the mineral was first found.
Occurrence In saline lake deposits in arid regions.

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

What is Colemanite?

Colemanite serves as an ore for boron and has many industrial uses.

Does Colemanite Make a Good Jewelry Stone?

Colemanite has weak dispersion, so it shows little fire, and normally occurs colorless. Since it also has perfect cleavage and a hardness of only 4.5, this fragile gem would make an unlikely choice for a jewelry stone. Ring use would require a protective setting. Other uses, such as in earrings, pendants, or brooches, would be more practical.

Colemanites have considerable heat sensitivity, so jewelers should take great care placing these gems in metal settings.

Colemanite: California (1.4). Photo © Joel E. Arem, PhD, FGA. Used with permission.

Identifying Colemanites

Colemanites are both pyroelectric and piezoelectric. They generate an electric current when heated or placed under pressure, respectively.

Faceted colemanites may show facet doubling due to their birefringence.

This large, eye-clean, custom shield-cut colemanite displays the facet doubling effect very nicely. 9.33 cts, 14 x 12.1 mm, Boron, California. © The Gem Trader. Used with permission.

Are There Synthetic Colemanites?

Scientists have synthesized colemanites for a variety of research projects, including studies of their electrical properties. However, there’s no known jewelry use for this lab-created material.

Colemanites don’t usually receive any known gemstone treatments.

Where are Colemanites Found?

The southwestern United States, particularly Boron and Death Valley, California, produces beautiful colemanite crystals. Other notable sources include Argentina, Kazakhstan, and Turkey.

colemanites - Turkey

This crystal specimen contains gemmy, honey brown colemanites with “second generation” colorless colemanites on their edges. 5.4 x 5.0 x 3.7 cm, Kestelek Mine, Mustafa Kemalpafla, Bursa Province, Marmara Region, Turkey. © Rob Lavinsky, www.iRocks.com. Used with permission.

Stone Sizes

Large crystals and masses could yield gems of 50-100 carats. Crystals normally range up to about 1 inch in size.

  • Smithsonian Institution (Washington, DC): 14.9 (California).

Caring for Colemanite

Colemanites are slightly soluble in water. Don’t soak these gems during cleaning. Make sure to pat them dry before storing. Clean them only with a soft brush, mild detergent, and warm water. For more care recommendations, consult our gemstone jewelry cleaning guide.

colemanites rough and cut set - California

This colemanite rough and cut set features a cluster of tabular crystals and a faceted, 2.47-ct, 8 mm gemstone. Boron, Kramer District, Kern Co., California, USA. © Rob Lavinsky, www.iRocks.com. Used with permission.

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