Types Of Asbestos Fibers

Chrysotile Asbestos is Common in Consumer Products

Asbestos is the generic name for six naturally occurring minerals that have been used in commercial products for their strength, flexibility, low electrical conductivity, and resistance to heat and chemicals. It is composed of silicon, oxygen, hydrogen, and various metals.

Asbestos can be divided into two basic groups, serpentine and amphibole, which differ in their physical characteristics. Serpentine asbestos develops in a layered or tiered form, whereas amphibole asbestos has a chain-like structure.

Identification

Asbestos is generally made up of fiber bundles which easily separate into long, thin fibers. Positive identification of a specific fiber type requires microscopic analysis and examination. All asbestos fibers are hazardous to human health.

Asbestos Types

There are six types of asbestos minerals that occur naturally within the Earth's environment. The Environmental Protection Agency (EPA) has classified the types as such:

Chrysotile : Chrysotile is one of the most common and most dangerous forms of asbestos found within our Earth. This type of asbestos accounts for approximately 90 percent of commercially-used asbestos in the world. Chrysotile asbestos fibers are long, white, and curly.

Amosite : Amosite asbestos is recognized by its straight fibers and brown color. Amosite asbestos contains iron and magnesium, and was most used within different types of insulation products. The EPA has determined amosite to be the second most used type of asbestos in the United States.

Crocidolite : Crocidolite takes the form of blue, straight fibers. It is a sodium iron magnesium silicate, and is considered to be the most dangerous type of asbestos due to its physical properties.

Tremolite : Tremolite asbestos fibers can be brown, gray, white or green, and like other types, can also be translucent. Tremolite was not mined or used commercially on its own, but could often be found contaminating other minerals, such as chrysotile, vermiculite and talc.

Anthophyllite : Like tremolite asbestos, anthophyllite minerals were not sought out for their commercial use, but instead found their way into products made with vermiculite and talc. The miners of vermiculite and talc are at high risk for developing asbestos-related diseases because of anthophyllite contamination within the substances they mined. Anthophyllite asbestos can range in color from white to gray to brown.

Actinolite : Actinolite asbestos appears as dark green crystals or fibrous aggregates. Like tremolite and anthophyllite, actinolite asbestos is often found as a contaminate within different commercial asbestos products. It has been found in paints, sealants, children's toys, and more.

While these six types of asbestos have physical and chemical differences, they are all known carcinogens proven to be hazardous to human health.

Geographic Occurrence

Major asbestos deposits can be found in rock formations in the United States, Canada, South Africa, and the former Soviet Union. In the United States, asbestos occurs in 20 states and has been mined in 17 states (Asbestos Facts, U.S. Geological Survey). Serpentinite, the most common source for chrysotile, is present in the Appalachians, Cascades, Coast Ranges of California and Oregon, and in other mountainous areas.

Currently, chrysotile is the only type of asbestos mined on a large scale. Small amounts of tremolite asbestos are still mined in India. Commercial production of crocidolite and amosite has ended in South Africa.