HYDROBORACITE

    Class : Carbonates, nitrates, borates
    Subclass : Borates
    Crystal system : Monoclinic
    Chemistry : CaMgB6O8(OH)6 3H2O
    Rarity : Uncommon

Hydroboracite is a mineral typical of salt deposits resulting from the evaporation of salt lakes. It is the classic companion of colemanite, ulexite and priceite. Its name refers to its chemical composition : from the Greek hudôr (water) and its formerly supposed analogy with boracite. Hydroboracite is white in color, rarely brownish or greenish, and constitutes concretionary masses with a fibroradiated texture or elongated lamellar crystals. The resemblance with certain aragonites or fibrous gypsums can be strong. It is a secondary boron ore.

Main photo : 3.5 cm hydroboracite from Kohnstein Quarry, Niedersachswerfen, Germany © Rob Lavinsky

Hydroboracite from Furnace Creek, California, USA © Rob Lavinsky
Hydroboracite from Kohnstein Quarry, Niedersachswerfen, Germany © Rob Lavinsky
Hydroboracite from Death Valley, California, USA © Enrico Bonacina
Hydroboracite from Rio Tinto, Boron, California, USA © Gianfranco Ciccolini

Hydroboracite in the World

Hydroboracite is known in beautiful geodic crystals at Boron (California), a deposit which also yielded a mass of pure hydroboracite of more than a ton, and at Stassfurt and Kohnstein Quarry (Germany) with transparent crystals of more than 3 cm. This mineral is also present in Furnace Creek (Death Valley, California) and in quite a few Canadian salt deposits, as well as in the Chilean and Argentinian salt flats.

Hydroboracite in France

Hydroboracite is not present in the French underground.

Twinning

No twin known for this mineral species.

Fakes and treatments

No fakes recorded for this mineral species.


Hardness : 2 to 3
Density : 2.15 to 2.17
Fracture : Undetermined
Streak : White

TP : Translucent to transparent
RI : 1.520 to 1.571
Birefringence : 0.049
Optical character : Biaxial -
Pleochroism : None
Fluorescence : None

Solubility : Acids

Magnetism : NoneRadioactivity : None