Brucite - Encyclopedia

    Class : Oxides and Hydroxides
    Subclass : Hydroxides
    Crystal system : Rhombohedral
    Chemistry : Mg(OH)2
    Rarity : Quite common

Brucite is a low temperature hydrothermal hydroxide. It is a product resulting from the serpentinization of peridotites which can also form veins in metamorphic limestones and chloritoschists. Brucite owes its name to the American physicist and mineralogist Archibald Bruce, founder of the American Mineralogical Journal, who first observed it in 1814. It is generally in lamellar or foliated masses, undulating, rarely spherical with a low hardness (2.5), reminiscent ofgypsum ; it can also be fibrous (nemalite variety) with separable and elastic fibers up to 50 cm in size. It is also common in stacking hexagonal tabular crystals (each crystal can measure up to 20 cm) and are gathered in colorless or white subparallel aggregates, brucite can also be green, yellow, or blue. By its geology, it is a mineral that only very rarely occurs in aesthetic and developed formations. It is a very accessory mineral of magnesium but also a mineral that enters in the composition of magnesium refractories (ceramics resistant to high temperatures). It should also be noted that some brucites of translucent to semi-transparent quality have been cut in faceted gemstones but this is only reserved for the gemstones collector's.

Brucite from Killa Saifullah District, Balochistan, Pakistan
Brucite from Killa Saifullah District, Balochistan, Pakistan
Brucite from Killa Saifullah District, Balochistan, Pakistan
Brucite from Killa Saifullah District, Balochistan, Pakistan

Brucite in the World

Beautiful samples of brucite come from Tilly Foster (New York) and Wood (Pennsylvania) chromite mine where large crystals dot the chromite lenses. Magnificent crystals larger than 5 cm were extracted from the Abest mine near Iekaterinburg (Russia) and very good specimens from the Kempirsay mine still in the Ural Mountains. Excellent crystals are also reported in chloritoschists of Zimbabwe near Mutorashanga. The carbonatite from Palabora (South Africa) has also produced superb masses of blue brucite weighing several kilograms. The most beautiful brucite formations however come from Killa Saifullah in Pakistan (right picture), discovered in 2017 these brucites form centimetric balls of a bright yellow can constitute sets of more than 20 cm ! This discovery redefined the TOP for the species.

Brucite in France

France has some deposits where brucite has been reported especially in skarns of Costabonne in the Pyrenees but also in the cipolins of Arignac.

Fakes and scams

No fakes reported for this mineral species.

Hardness : 2.5
Density : 2.39
Fracture : Irregular
Trace : White

TP : Translucent to transparent
IR : 1.56 to 1.60
Birefringence : 0.02
Optical character : Uniaxe -
Pleochroism : None
Fluorescence : White to blue

Solubility : Hydrochloric acid

Magnetism : None
Radioactivity : None