boracite
Sign in to saveBoracite is a magnesium borate mineral with formula: Mg3B7O13Cl. It occurs as blue green, colorless, gray, yellow to white crystals in the orthorhombic - pyramidal crystal system. Boracite also shows pseudo-isometric cubical and octahedral forms. These are thought to be the result of transition from an unstable high temperature isometric form on cooling. Penetration twins are not unusual. It occurs as well formed crystals and dispersed grains often embedded within gypsum and anhydrite crystals. It has a Mohs hardness of 7 to 7.5 and a specific gravity of 2.9. Refractive index values are nα = 1
Key facts
- Mineral.name
- Boracite
- Mineral.image
- Boracite-169813.jpg
- Mineral.imagesize
- 260px
- Mineral.category
- Tektoborates
- Mineral.formula
- Mg3B7O13Cl
- Mineral.IMAsymbol
- Boc
- Mineral.molweight
- 392.03 g/mol
- Mineral.strunz
- 6.GA.05
- Mineral.dana
- 25.06.01.01
- Mineral.system
- Orthorhombic
- Mineral.class
- Pyramidal (mm2) (same H-M symbol)
- Mineral.symmetry
- Pca21
- Mineral.unit cell
- a = 8.577(6) Å, b = 8.553(8) Å, c = 12.09(1) Å; Z = 4
- Mineral.color
- Colorless, white, gray, brown, orange, yellow, pale green, dark green, blue-green, or blue; colorless in transmitted light
- Mineral.habit
- Crystalline, disseminated (pseudocubic)
- Mineral.twinning
- Rarely as penetration twins
- Mineral.cleavage
- None
- Mineral.fracture
- Irregular/uneven, conchoidal
via Wikipedia infobox
Wikidata facts
- Image
- Boracit mineralogisches museum bonn.jpg
Show 6 more facts
- Strunz 8th edition (series ID, updated)
- Vc/E.02
- Nickel-Strunz 9th edition (updated 2009)
- 6.GA.05
- Commons category
- Boracite
- Nickel-Strunz '10th ed', review of (9th ed/ 2009 update)
- 6.GA.05
- chemical formula
- Mg₃B₇O₁₃Cl
- IMA Mineral Symbol
- Boc
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- References
- External links
Boracite is a magnesium borate mineral with formula: Mg3B7O13Cl. It occurs as blue green, colorless, gray, yellow to white crystals in the orthorhombic - pyramidal crystal system. Boracite also shows pseudo-isometric cubical and octahedral forms. These are thought to be the result of transition from an unstable high temperature isometric form on cooling. Penetration twins are not unusual. It occurs as well formed crystals and dispersed grains often embedded within gypsum and anhydrite crystals. It has a Mohs hardness of 7 to 7.5 and a specific gravity of 2.9. Refractive index values are nα = 1.658 - 1.662, nβ = 1.662 - 1.667 and nγ = 1.668 - 1.673. It has a conchoidal fracture and does not show cleavage. It is insoluble in water (not to be confused with borax, which is soluble in water).
Boracite is typically found in evaporite sequences associated with gypsum, anhydrite, halite, sylvite, carnallite, kainite and hilgardite. It was first described in 1789 for specimens from its type locality of Kalkberg hill, Lüneburg, Lower Saxony, Germany. It is also found near Sussex, New Brunswick.
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