Amphibole

The amphiboles are a family of mineral, Silicate S of Fer, Calcium or Magnésium. They crystallize in the systems orthorhombic and monoclinical in prisms very lengthened, with a typical cleavage according to the faces of the prism. They belong to the group of the Inosilicate S.

Very largely widespread in nature, they are generally of dark color, but can vary white with the black. In general, they are mineral hard and heavy. They enter partly the constitution of the magmatic rocks and metamorphic.

Certain rocks called Amphibolite S are made up almost entirely of amphiboles.

The amphiboles are characterized by the anion 7  - and in particular by the presence of water. Indeed they are minerals hydrated contrary to the pyroxenes. One can macroscopically distinguish amphiboles thanks to their cleavages with 120°Contrairement with pyroxenes which have a Clivage with 90°.

Among the various varieties of amphiboles, one distinguishes ferromagnesic amphiboles, calcic amphiboles and sodic amphiboles.

Amphiboles ferromagnésiennes

Orthorhombic S

  • Anthophyllite, rich in magnesium and iron.
  • Gédrite, rich in aluminum, of fibrous structure, discovered with Gedres , in the Ardeche and the the Rhone.
  • Holmquistite, rich in Lithium

Monoclinical S

  • Cummingtonite, rich in iron and magnesium, discovered with Cunnington with the the United States, in alpine solid masses and préalpins, and in the VAr, accompanied by Garnet-red S, Magnetite and quartz.
  • Grünérite, rich in iron, of dark color green, discovered by French chemist L.E Gruener

Calcic amphiboles Monoclinical S

They contain magnesium, iron and calcium

  • actinolite, rich in iron, of color clear green to dark green, crystals with acicular structure (in the shape of needle), is in the limestones modified in contact with the eruptive rocks, discovered in all the alpine chain of the Europe.

    • nephritis , of color gray-white to the constant green; it is one of the two forms of Jade (the other being the Jadéite, a Pyroxène);
    • byssolite , a variety with fibrous structure;

  • Tremolite or Asbestos of amphibole , rich in magnesium, of white color, discovered in the Valley of Trémola , in Swiss. It is in the limestones modified in contact with the eruptive rocks. In France one finds it in the Ariège, in Haute-Garonne, Isere, with Arnave, Chamonix, Tarascon and Trimouns.

  • Hornblende, rich in iron, of almost black color, discovered in Germany.
    • Pargasite, magnesium and iron, discovered with Pargas in Finland.
    • Kaersutite, rich in titanium, discovered with Kaersut with the Greenland.

Sodic amphiboles Monoclinical S

They contain sodium but not calcium.

  • Glaucophane discovered in Brittany, in the Island of Groix, in Saint-Véran (Hautes-Alpes) and Padula, Corsica Vezzani in .

  • Riebeckite, dark blue, discovered by the German explorer E. Riebeck. Present to Evisa, in Corsica.

Toxicity

Of prohibited use because of their toxicity, these rocks contain Amiante S such as the blue Amiante or Crocidolite, the brown Amiante or Amosite, the Trémolite, the Actinolite and the Anthophylite.

See too

external Bonds
  • http://www.chez.com/ericlecaplain2/Amphibole.html

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