Asbestos is a naturally occurring group of minerals that can be identified only under a microscope. It is a flexible, highly fire-resistant fiber which is very strong. It has been mined for years due to its useful properties related to thermal insulation, chemical and thermal stability and high tensile strength.
There are two types of asbestos based on the crystalline structure. The long thin fibers, amphibole, form a chain-like crystal structure. The serpentine asbestos is shorter, thicker and curlier. It has a layered, crystalline structure. The serpentine type of asbestos has only one member and it is chrysotile. Chrysotile makes up about 90 to 95% of the asbestos contained in U.S. buildings.
There are five members in the amphibole group: amosite, crocidolite, anthophyllite, tremolite and actinolite.
Amosite is the next most common form of asbestos found in buildings in the U.S., next to chrysotile. Amosite is also known as brown asbestos. Blue asbestos, or crocidolite, is the third most common form of this mineral. Anthophyllite, tremolite and actinolite are quite rare and are typically found in conjunction with other compounds of the other more common types of asbestos.
Asbestos is made up of microscopic packages that become airborne when disturbed. These fibers get into the air and then can be inhaled by people exposed to that air. These fibers can cause significant health problems, including malignant mesothelioma, because they become embedded in lung tissue and cannot be removed by the body's natural immune system.
This mineral may not always be an immediate hazard if it is not airborne. If asbestos can be properly maintained, it is recommended to be left alone with periodic inspections. It is only when these asbestos-containing materials get disturbed that they can become airborne and cause a problem.
In the asbestos industry, the term "friable asbestos" is used to describe asbestos that can be reduced to dust by hand pressure. Asbestos that is too hard to be reduced to dust by hand pressure is called "non-friable asbestos." Non-friable asbestos can be turned into the friable version by machine grinding, sanding or dry-buffing. Non-friable asbestos materials, which include items such as flooring and siding, are not regulated, as long as they do not become friable.
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