Boracite
Current inventory:  1 gem
 

  
Boracite's name refers to its Boron content.

Discovered in 1789;   IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

Mg₃B₇O₁₃Cl

Magnesium Borate Chloride

Molecular Weight:

392.03 gm

Composition:

Magnesium

18.60 %

Mg

30.84 %

MgO

Boron

19.30 %

B

62.15 %

B₂O₃

Chlorine

9.04 %

Cl

9.04 %

Cl

-

- %

Cl

-2.04 %

-O=Cl₂

Oxygen

53.06 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Borates

Strunz 8th Ed. ID:

5/L.04-10

Nickel-Strunz 10th Ed. ID:

6.GA.05

6 : BORATES
G : Heptaborates and other megaborates
A : Tekto-heptaborates

Related to:

Boracite Group. Boracite-Ericaite Series. The magnesium analogue of Ericaite and Chambersite. The orthorhombic dimorph of Trembathite.

Members of Group:

Boracite Group: Boracite, Chambersite, Congolite, Ericasite, Trembathite.

Varieties:

Bromboracit, Ferroan Boracite, Stassfurtite

Synonyms:

Alpha-boracite, b-Boracite, Beta-boracite, Boracite (of Werner), Borate of Magnesia, Metaboracite, Parasite

Crystal Data

Crystallography:

Orthorhombic - Pyramidal

Crystal Habit:

Euhedral crystals, to 2.5 cm, (referred to pseudotetrahedral morphology) and a dozen other modifying forms; spherulitic, plumose to fibrous, fine granular aggregates.

Twinning:

Rarely as penetration twins

Physical Properties

Cleavage:

None observed

Fracture:

Conchoidal to Irregular/Uneven

Tenacity:

Brittle

Moh's Hardness:

7.0 - 7.5

Density:

2.91 - 3.10 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Other: 

Very slowly decomposed by water. Slowly but completely soluble in HCl. Strongly piezoelectric and pyroelectric. At 265° the crystal system reverts to a high-temperature phase and the material becomes isotropic. Forms pseudomorphs after quartz (Douglashall).

Optical Properties

Color:

Pale green, greenish blue, blue, colorless, grey, white; dark green (ferroan)

Transparency:

Transparent, Translucent

Luster:

Adamantine to Vitreous

Refractive Index:

1.658 - 1.673  Biaxial ( + )

Birefringence:

0.010 - 0.011

Dispersion:

0.024 (weak)

Pleochroism:

None

Occurances

Geological Setting:

Bedded sedimentary deposits of gypsum and anhydrite; salt deposits; potash deposits of the oceanic type.

Common Associations:

Anhydrite, Carnallite, Danburite, Gypsum, Halite, Hilgardite, Kainite, Magnesite

Common Impurities:

Fe(II)

Type Locality:

Kalkberg hill, Lüneburg, Lower Saxony, Germany

Year Discovered:

1789

View mineral photos:

Boracte Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Boracite is one of the rarest of collector's gems. The only facetable crystals come from the Stassfurt and Hanover districts of Germany. Boracite crystals are very small and cut gems are usually very pale blue to green or colorless. Boracite is the magnesium analogue of Chambersite. Boracite is an evaporite mineral and is not surprisingly found with other evaporite minerals like Anhydrite, Gypsum and Halite. Boracite crystals are often embedded in these other evaporite minerals.

Locations for Boracite are in Germany, from Lüneburg, 40 km south-southeast of Hamburg, Lower Saxony; in Saxony-Anhalt, in the Stassfurt-Westeregeln-Bernburg district, at the Douglashall, Berlepsch, Solvayhall, Wilhelmshall and other mines; in Thuringia, from Bischofferode, in the Glückauf mine, Sondershausen, and elsewhere. In France, at Lunéville, Meurthe-et-Moselle. In the Boulby potash mine, northwest of Whitby, Yorkshire, England. In the Chelkar salt dome, Ak-sai Valley, Uralsk district, Kazakhstan. Large crystals from Alto Chapare, Cochabamba, Bolivia. In the USA, in the Choctaw salt dome, Iberville Parish, Louisiana, and the Louann Salt Formation, Clarke County, Alabama. From the Penobsquis and Salt Springs evaporite deposits, near Sussex, New Brunswick, Canada.
 

  
Boracite gems for sale: