BUSTAMITE

    Class : Silicates
    Subclass : Inosilicates
    Crystal system : Triclinic
    Chemistry : CaMnSi2O6
    Rarity : Uncommon

Bustamite belongs to the group of pyroxenoids. It has a structure identical to that of wollastonite and strongly resembles rhodonite, with which it often shares deposits but from which it differs by a high calcium content (12 to 25% CaO). Its chemistry is also quite variable, iron, magnesium and zinc being able to enter into its composition. It is found in manganiferous skarns or metamorphic manganese deposits, sometimes in manganese hydrothermal veins. It owes its name to the Mexican General Anastasio Bustamente who discovered the mineral. Bustamite crystals may evoke rhodonite, but more commonly radiating groups of flattened lamellae or fine acicular crystals, pinkish to red in color, turning brown and then black by surface oxidation are more commonly observed.

Main photo : Bustamite from Broken Hill, New South Wales, Australia © Weinrich Mineral

Bustamite from Broken Hill, New South Wales, Australia © John Haupt
Bustamite from Broken Hill, New South Wales, Australia © Eugene & Sharon Cisneros
Bustamite from Broken Hill, New South Wales, Australia © Weinrich Mineral
1.99 ct bustamite from South Africa

Bustamite in the World

Australia's Broken Hill mine has yielded the finest crystals known, gemstone pink-red crystals that can exceed 2.5 cm. Magnificent banded masses used in decoration and geodic crystals exceeding 2 cm were extracted from the N'Chwaning mine (South Africa). The large manganese mines at Franklin and Sterling Hill (New Jersey) also yielded good samples. The "type" definition samples from the Tetela de Ocampo site (Mexico), on the other hand, are mixtures of johannsenite and rhodonite.

Right photo : Bustamite from Franklin Mine, New Jersey, USA © Rock Currier


Bustamite in France

Bustamite is present at Mine Coustou and in the Aure Valley (Hautes-Pyrénées).

Twinning

Twin known on {110} but rare.

Fakes and treatments

No fake identified for this mineral species.


Hardness : 5.5 to 6.5
Density : 3.3 to 3.4
Fracture : Irregular
Streak : White

TP : Translucent to transparent
RI : 1.640 to 1.710
Birefringence : 0.015
Optical character : Biaxial -
Pleochroism : Visible
Fluorescence : Red

Solubility : Hydrochloric acid

Magnetism : None
Radioactivity : None