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Hydroboracite
Current inventory:  0 gems
 

Chemistry:  CaMgB₆O₈(OH)₆·3(H₂O)  [Hydrated Calcium Magnesium Borate]

Discovered in 1834;   IMA status: Valid (pre-IMA; Grandfathered).
Hydroboracite is named in allusion to the composition, being a HYDRated BORAte.

Classification

Mineral Classification:

Borates

Strunz 8th Ed. ID:

5/J.03-20

Nickel-Strunz 10th Ed. ID:

6.CB.15

6 : BORATES
C : Triborates
B : Ino-triborates

Related to:

Colemanite - Hydroboracite Series

Crystal Data

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

As slender crystals, prismatic along [001] and flattened on {010}, to 10 cm; in fanlike to radial spherical aggregates and in swallowtail composites; as drusy coatings; compact, fine-grained.

Twinning:

None

Physical Properties

Cleavage:

[010] Perfect, [100] Distinct

Fracture:

Irregular/Uneven

Tenacity:

Brittle

Hardness (Mohs):

2.0 - 3.0; 5.0 - 6.0 in some specimens

Density:

2.15 - 2.17 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Other:

Virtually insoluble in cold water. Partially dissolved by prolonged submersion in boiling water.

Optical Properties

Color:

Colorless, White

Transparency:

Transparent to Translucent

Luster:

Vitreous; Silky if fibrous

Refractive Index:

1.520 - 1.571  Biaxial ( + )

Birefringence:

0.0490

Dispersion:

Relatively Weak; r < v

Pleochroism:

None

Occurances

Geological Setting:

Typically formed by groundwater alteration of Colemanite; may be primary.

Common Associations:

Colemanite, Tunellite, Ulexite

Type Locality:

Inder B deposit and salt dome, Atyrau (Gur'yev), Atyrau Oblysy (Atyrau Oblast'), Kazakhstan

Year Discovered:

1834

View mineral photos:

Hydroboracite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Hydroboracite is a rare borate mineral very similar to Ulexite. They both commonly form as silky, fibrous crystal clusters and are not easy to distinguish. Hydroboracite gems are very rare. Most crystals are fibrous and silky and not suitable for faceting.

The most notable occurances of Hydroboracite are: Kohnstein Quarry, Niedersachswerfen, Nordhausen, Harz Mts, Thuringia, Germany; Bigadiç Mine, Bigadiç, Balikesir Province, Marmara Region, Turkey; Boron Pit, U.S. Borax Mine, Boron, Kramer District, Kern County, California, USA; and Death Valley, San Bernardino County, California, USA.
 

  
Hydroboracite gems for sale:

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