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Intergrown Cubic Boracite Crystal

The Mineral boracite

Boracite describes both a mineral group as well as an individual mineral within that group. The Boracite group is a solid solution series of chloro-borates, with Boracite, Chambersite, and Ericaite, as the main members. Boracite is the magnesium-rich end member, and the most prevalent mineral of this group.

Boracite is known for its equidimensional crystals, which may form in unique habits not seen elsewhere in the mineral kingdom. Up until recently, Boracite crystals were generally isolated small crystals, but a find in the Boulby Mine in England has produced large crystal groups much different then previous discoveries of this mineral. Boracite is named after its membership within the borate group, containing the element boron in its chemical composition.
Chemical Formula Mg3B7O13Cl
Composition Magnesium chloro-borate, sometimes with iron and manganese
Variable Formula (Mg,Fe,Mn)3B7O13Cl
Color Colorless, light blue, green, grayish-green, sea-green. Rarely red, pink, or yellow.
Streak White
Hardness 7 - 7.5
Crystal System Orthorhombic
3D Crystal Atlas
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Crystal Forms
and Aggregates
Crystals are in cubic, dodecahedral, or tetrahedral habit, often with modifications. Crystals convert to an orthorhombic crystal structure upon cooling after their formation, though the isometric shape is preserved. Crystals may be in individual floater crystals, as well as in groups of crystals.
Transparency Transparent to translucent
Specific Gravity 2.9 - 3.0
Luster Adamantine, vitreous
Cleavage None
Fracture Uneven
Tenacity Brittle
Other ID Marks Weak greenish fluorescence in shortwave ultraviolet light.
In Group Borates; Anhydrous Borates
Striking Features Crystal habits, hardness, and mode of occurrence
Environment In marine evaporite deposits including salt domes.
Rock Type Sedimentary
Popularity (1-4) 3
Prevalence (1-3) 3
Demand (1-3) 2


 -  A fibrous variety of Boracite from the potash deposits of Stassfurt, Germany.

Boracite is a rare collector's mineral, and small crystals make highly collectible specimens for thumbnail collectors.

A classic locality for Boracite crystals, in green and grayish-green equidimensional crystals, is the potash deposits of Bernburg and Stassfurt in Saxony-Anhalt, Germany. Single floater crystals, in dodecahedral or modified cubic form, have come from  from Lüneburger, Niedersachsen (Lower Saxony), Germany. Transparent green Boracite crystals, mostly in tetrahedral form, have come from the Glückauf Mine, Sondershausen, Thuringia, Germany.

A more recent find of Boracite is at the Boulby Mine, Loftus, North Yorkshire, England. This locality has produced sea-green crystals, in large clusters many times larger than all previous finds of this mineral. Another recent and important producer of Boracite is Alto Chapare, Cochabamba Department, Bolivia. Crystals from this mine are in cubic form with poor transparency, and usually in matrix. The color ranges from grayish-green to a less common peachy pink.  

Halite, Anhydrite, Gypsum

boracite PHOTOS
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