Light bluish green boracite, 0.33 cts, 4.3 mm, square cut, Lower Saxony, Germany. © The Gem Trader. Used with permission.
With light blue and green colors, no cleavage, and high hardness, boracite is an uncommon mineral. Unfortunately for jewelry lovers, faceted boracites are very rare.
| Data | Value |
|---|---|
| Name | Boracite |
| Crystallography | Orthorhombic. Pseudo-tetragonal. Crystals small and equant. |
| Refractive Index | 1.658-1.673 |
| Colors | Colorless, white, gray, orange, yellow, pale to dark green, bluish green, pink (very rare). |
| Luster | Vitreous. |
| Hardness | 7-7.5. |
| Wearability | Good |
| Fracture | Conchoidal to uneven |
| Specific Gravity | 2.95 |
| Birefringence | 0.010-0.011 |
| Cleavage | None |
| Dispersion | 0.024 |
| Luminescence | Weak greenish (SW) |
| Luminescence Present | Yes |
| Luminescence Type | Fluorescent, UV-Short |
| Transparency | Translucent to transparent. |
| Absorption Spectrum | Not diagnostic. |
| Formula | Mg3B7O13Cl |
| Pleochroism | None. |
| Optics | α = 1.658-1.662; β = 1.662-1.667; γ = 1.668-1.673. Biaxial (+), 2V =82°. |
| Optic Sign | Biaxial + |
| Etymology | Named after the boron in its composition. |
| Occurrence | Secondary deposits formed in evaporite sequences (seawater). |
Boracite, Kalkberg Hill, Luneburg, Lower Saxony, Germany, (type locality). © Rob Lavinsky, www.iRocks.com. Used with permission.
Aqua-colored boracites, crystals about 2 mm across, specimen 5.8 x 3.2 x 1.8 cm. Boulby Mine, Loftus, North Yorkshire, England, UK. © Rob Lavinsky, www.iRocks.com. Used with permission.
Boracite forms in salt deposits and similar environments as a result of seawater evaporation in enclosed basins. Rare cut boracites can show delicate shades of blue, green, yellow, white, and grey and have moderate dispersion. Some stones are colorless.
Boracite, 0.21 cts. Photo © Joel E. Arem, PhD, FGA. Used with permission.
Under physical pressure, boracite generates an electric charge. This is known as known the piezoelectric effect. This mineral also exhibits the pyroelectric effect. It generates an electric charge when heated.
Boracites decompose slowly in water.
Scientists have synthesized boracites for various purposes, including research into its electrical properties as well as radioactive waste storage. However, there’s no known jewelry use for this synthetic material.
Cuttable crystals occur only in the Stassfurt and Hanover districts of Germany, which usually yield small, pale crystals.
Other notable gem sources include the following:
This boracites on matrix specimen contains pale blue-gray crystals as well as a single, rare orange-pink crystal. Alto Chapare District, Chapare Province, Cochabamba Department, Bolivia. © Rob Lavinsky, www.iRocks.com. Used with permission.
Boracite crystals are very small and usually yield gemstones ranging from 1-2 carats, so gems over 2 carats would be considered extreme rarities.
Although boracites react to water very slowly, keep them dry in storage, where they would otherwise have time to sit and decompose. Alcohol may be used in lieu of water for cleaning. Otherwise, since these stones have high hardness (7-7.5) and no cleavage, they require no special care. Consult our gemstone jewelry cleaning guide for more recommendations.
Boracite: Hanover, Germany (0.6). © Joel E. Arem, PhD, FGA. Used with permission.
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