Asbestos minerals

There are three major types of asbestos minerals, known as "white", "brown" and "blue" asbestos. The following description includes six asbestos minerals:

  • actinolite
  • amosite (brown asbestos)
  • anthophyllite
  • crocidolite (blue asbestos)
  • chrysotile (white asbestos)
  • tremolite

All asbestos minerals occur naturally, and most belong to the amphiboles. The exception is chrysotile, which is a serpentine mineral.

The amphiboles are a very common group of rock-forming silicate minerals. Theoretically, asbestos may be present in all metamorphic rocks containing Mg-Fe amphiboles or serpentine, where the rock has been subject to shear stress.

Asbestos is mined in open-pit mines in i.a. Canada, Russia and the U.S.A.

Chrysotile ("white asbestos")
Mg3[Si2O5](OH)4

Chrysotile is the most widely used industrial asbestos mineral, with the following characteristics:

  • Has bent fibers, often as bundles that split into fine fibrils
  • Can be spun for use in textiles
  • Can be used for adsorption of gases and solvents
  • High tensile strength
  • High thermal and electrical insulation capacity

Chrysotile is the only asbestos mineral that has a low resistance to acids, but a high resistance to bases. Chrysotile has been used in asbestos cement, fireproofing, gaskets, adhesives, putty, joints, textiles, mats, paint etc.

Anthophyllite
Mg7[Si8O22](OH)2

  • Straight fibers that split in the ends, forms bundles.
  • High chemical resistance
  • High thermal and electrical insulation capacity

Has been used in, e.g. insulation material, adhesives, plastics, filling materials and reinforcement material etc.

Tremolite and actinolite
Ca2(Mg, Fe2+)5[Si8O22](OH)2

Tremolite contains calcium (Ca) and magnesium (Mg), whereas in actinolite, Mg is replaced by iron (Fe). Both minerals occur as asbestiform and non-asbestiform.

  • Straight fibers, that split in the ends (asbestos), but also as fibers with the ratio length:thickness <3
  • Occurs only in natural materials: talc, dolomite etc.

Amosite ("brown asbestos")
Fe7[Si8O22](OH)2

Amosite is a trade name for the amphiboles belonging to the cummingtonite - grunerite solid solution series. It is named as an acronym from Asbestos Mines of South Africa. Amosite is stable up to temperatures of 600 – 900 ºC. Amosite can be found in e.g. pipe insulation material and fireproofing.  

  • Straight fibers that split in the ends
  • Forms bundles
  • Can be spun
  • High tensile strength (but not as high as chrysotile or crocidolite)

Crocidolite ("blue asbestos")
Na2Fe5[Si8O22](OH)2

  • Crocidolite forms very fine fibers. The fibers split in the ends and can form bundles.
  • High tensile strength
  • Can be spun

Crocidolite can be found in asbest-cement products, filters, gaskets and insulation etc.

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