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| Boracite
was named in 1789 by Abraham Gottlob Werner (1749-1817), a professor of mining and mineralogy at the Freiberg Mining Academy,
Germany, for its Boron content.
| Discovered
in 1789;
IMA
status: Valid (pre-IMA; Grandfathered) |
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Chemistry
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Chemical
Formula: |
Mg3B7O13Cl
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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 |
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Oxygen |
53.06 % |
O |
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|
100.00 % |
|
100.00 % |
= TOTAL OXIDE |
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Classification
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Mineral
Classification: |
Borates |
Strunz 8th
Ed. ID:
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5/L.04-10
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Nickel-Strunz 10th
Ed. ID:
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6.GA.05
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6 : BORATES
G : Heptaborates and other megaborates A :
Tekto-heptaborates
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Related
to: |
Boracite Group. Boracite-Ericaite Series. The magnesium analogue of Ericaite and Chambersite. The orthorhombic dimorph of Trembathite.
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Members
of Group: |
Boracite
Group: Boracite, Chambersite, Congolite, Ericasite, Trembathite.
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Varieties: |
Bromboracit,
Ferroan Boracite, Stassfurtite
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Synonyms: |
Alpha-boracite,
b-Boracite, Beta-boracite, Boracite (of Werner), Borate of Magnesia,
Metaboracite, Parasite
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Crystal
Data
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Crystallography:
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Orthorhombic
- Pyramidal
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Crystal
Habit:
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Euhedral
crystals, to 2.5 cm, (referred to pseudotetrahedral
morphology) and a dozen other modifying forms; spherulitic,
plumose to fibrous, fine granular aggregates.
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Twinning:
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Rarely
as penetration twins
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Physical
Properties
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|
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Cleavage: |
None
observed
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Fracture: |
Conchoidal
to Irregular/Uneven
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Tenacity:
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Brittle
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Moh's
Hardness: |
7.0
- 7.5
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Density:
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2.91 - 3.10 (g/cm3)
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Luminescence:
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None
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Radioactivity:
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Not
Radioactive
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Other: |
Strongly piezoelectric
and pyroelectric.
Very
slowly decomposed by water. Slowly but completely soluble in HCl. At 265° the crystal system reverts to a high-temperature phase and the material becomes isotropic.
Forms pseudomorphs after quartz (Douglashall).
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Optical
Properties
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Color: |
Pale
green, greenish blue, blue, colorless, grey, white; dark green (ferroan)
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Transparency: |
Transparent,
Translucent |
Luster: |
Adamantine
to Vitreous
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Refractive
Index: |
1.658 - 1.673 Biaxial
( + ) |
Birefringence: |
0.010 - 0.011
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Dispersion: |
0.024
(weak)
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Pleochroism: |
None
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Occurances
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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)
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Type
Locality: |
Kalkberg hill, Lüneburg, Lower Saxony, Germany
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Year
Discovered: |
1789
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View
mineral photos: |
Boracte
Mineral Photos and Locations |
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Unusual
Gem Categories
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Piezoelectric
Gems, Pyroelectric
Gems, Water
Soluble Gems |
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More
Information
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Mindat.org
Webmineral.com
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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.
Boracite
is one of the rare minerals that exhibit both the piezoelectric
effect and the pyroelectric effect. Piezoelectricity is the ability of some
mineral crystals to generate a voltage in response to applied mechanical
stress such as an external pressure or stress. Piezoelectricity was discovered in 1880 by French physicists, brothers Jacques and Pierre Curie. Pyroelectricity is the ability of certain mineral
crystals to generate an electrical
charge when they are heated or cooled. The first reference to the pyroelectric effect is in writings by Theophrastus in 314 BC, who noted that Tourmaline becomes charged when
heated. Sir David
Brewster gave the effect the name it has today in 1824. Both William Thomson in 1878 and Voight in 1897 helped develop a theory for the processes behind
pyroelectricity. Boracite is also a water
soluble mineral.
Boracite distribution:
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.
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Boracite
gems for sale:
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Gem:
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Boracite |
Stock
#:
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BORA-001 |
Weight:
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0.1725
ct |
Size: |
3.50
x 3.50 x 2.34 mm |
Shape: |
Trilliant |
Color: |
Colorless |
Clarity: |
Eye
clean |
Origin: |
Germany |
Treatment: |
None
(natural) |
Price: |
$104.00
[
Make an offer ]
|
Pictures
are of the actual gem offered for
sale. Gem images are magnified to
show detail. |
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Even
though this gem is small, it is relatively
large for the type. A very rare gem
that is eye clean and would be an interesting
addition to any gem collection.
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Gem:
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Boracite |
Stock
#:
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BORA-002 |
Weight:
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0.1375
ct |
Size: |
3.33
x 2.11 mm |
Shape: |
Trilliant |
Color: |
Colorless |
Clarity: |
Eye
clean to VVS2 |
Origin: |
Germany |
Treatment: |
None
(natural) |
Price: |
SOLD
(but we have others) |
Pictures
are of the actual gem offered for
sale. Gem images are magnified to
show detail. |
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A
small but beautiful gem that is not
often found as a round gem. A very nicely
faceted Boracite.
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