There are several types of asbestos fibers, of which three have been used for commercial applications: (1) Chrysotile, or white asbestos, comes mainly from Canada, and has been very widely used in the US. It is white-gray in color and found in serpentine rock. (2) Amosite, or brown asbestos, comes from southern Africa. (3) Crocidolite, or blue asbestos, comes from southern Africa and Australia. Amosite and crocidolite are called amphiboles. This term refers to the nature of their geologic formation.
Asbestos fibers belong to two separate mineral groups, known as:
- Chrysotile: contains only one asbestos variety, also known as serpentine
- Amphibole: contains five asbestiform varieties characterized by their needle-like appearance:
- Grunerite (amosite)
- Riebeckite (crocidolite)
The U.S. Bureau of Mines has listed more than 100 mineral fibers as asbestos-like, but the United States government only regulates the six aforementioned forms—primarily due to effective lobbying on behalf of the asbestos and stone industries.
These very fine fibers are separable, hundreds of times thinner than human hairs, and too small to be seen with the naked eye.
The Occupational Safety and Health Administration (OSHA) defines fibers of concern as at least five micrometers long and at least three times as long as their diameters.
Chrysotile (white asbestos)
The Serpentine asbestos Chrysotile, comes from the mining of the white serpentinite rocks which are common globally. It is:
- The most commonly used type, accounting for about 95 percent of the asbestos found in buildings in the U.S.
- Very flexible and can be used in a variety of construction materials for housing and commercial applications and also woven into fabric.
Amphiboles (brown, blue and green asbestos)
Anthophyllite is identified by its brittle white fibers:
- Formed by the breakdown of talc
- Not often used for industrial purposes
- Occasionally found in natural minerals that expand when heated, such as vermiculite, a gardening soil additive
Amosite is brown in color. Its name comes from an acronym for Asbestos Mines of South Africa. Although banned now in most countries, it was the second most commonly used type of asbestos. It is most frequently found in:
- Insulation materials
- Ceiling tiles
Crocidolite is named because of its blue fibers. It is believed to be the most deadly form of asbestos and is no longer mined. It occurs naturally in Australia, South Africa, Bolivia and the former Soviet Union. Fortunately, its commercial utility was limited compared to other types of asbestos and primary use was in cement and not insulation.
- Estimates are that almost 20 percent of miners of crocidolite have died from mesothelioma
Tremolite can be white or green and is found in most metamorphic rocks:
- Most often found as a contaminant in mined and processed chrysolite fiber
- Used by itself, but not frequently, for industrial purposes
- Identified as an ingredient in talcum powder
- Major asbestos in the infamous vermiculite mine in Libby, Montana
Actinolite is also found in metamorphic rocks and can be green, white, or gray:
- Rarely used commercially
- Non-fibrous variants do not pose health threats
Inhalation of any of the above fibers has been shown to cause disease. While a naturally occurring and common mineral, asbestos is friable when mined or used in products. Fibers continue to become airborne and pose significant health risks.
This is why even if you have no symptoms of asbestos exposure disease, if you believe you or a loved one has been exposed, you need to know:
- If you have been exposed, i.e., the place that concerns you should be tested
- The nature of the exposure
- How to have existing asbestos safely removed from where you live or work