Chrysotile (White Asbestos)
Chrysotile asbestos was used predominantly in products manufactured in the United States. Although small amounts of chrysotile were mined in the United States, the overwhelming majority of the mesothelioma causing asbestos was mined in Canada and then shipped into the United States.
Chrysotile asbestos is also known as serpentine because it is found in serpentine rock.
Serpentine is a polymorphous, magnesium-rich mineral typically found in metamorphic rocks. Its non-fibrous modifications are known as lizardite and antigorite, and the fibrous type is called chrysotile. Chrysotile fibers are formed by sheetlike crystals that roll into tight tubes and may exhibit several forms. The fibers may be compared to fine threads or hairs. Chrysotile usually occurs in bundles.
Amosite (Gray Asbestos)
Asbestiform Grunerite, (Fe2+,Mg)7[Si8 O22](OH)2
Amosite asbestos was used to a lesser extent than chrysotile. Most of the amosite asbestos used in the United States was mined in South Africa. The name “amosite” derives from the “asbestos mines of South Afica”.
Amosite asbestos is an amphibole. Grunerite is the mineralogically correct name used for amphiboles of the cummingtonite-grunerite series in which iron is predominant over magnesium (70% or more Fe / [Fe+Mg]).
Crystals of grunerite range in morphology from relatively thick, flat prisms to acicular, brittle grains, to very long, thin fibers and fiber bundles. The long thin fibers are moderately brittle and often bend in wide arches. Bundles of grunerite tend to separate into smaller groups of needlelike fibers. Because grunerite fibers do not normally fray or have split ends, but rather have flat or knifelike ends, the needlelike morphology may help to distinguish this amphibole from chrysotile. Forms of bundles resembling “broom tails” are also common. Small thin fragments of the mineral are common in some building materials.
Crocidolite (Blue Asbestos)
Asbestiform Riebeckite, Na2Fe3+2Fe2+3[Si8 O22](OH)2
Crocidolite asbestos was the least used in commercial products. Approximately 10% of the asbestos used in the United States was crocidolite.
Crocidolite is the asbestiform variety of riebeckite. Riebeckite is the name used for minerals of the glaucophane-crossite-riebeckite series in which iron is predominant over magnesium and aluminum. Crocidolite is called the “Blue Asbestos”, because it is strongly pleochroic, ranging from Prussian blue and indigo blue to yellow green.
The characteristic form of crocidolite is similar to that of chrysotile. The fibers generally resemble strands of fine textured hair and are slightly more brittle than chrysotile, but can usually bend beyond 90 degrees before breaking. Typically curved, hairlike, but straight fibers and bundles may also be found. Riebeckite cleavage fragments may be found in association with true asbestiform bundles. Crocidolite is harder than the other varieties of amphibole asbestos.
Asbestosis is a scarring of the lung manifested by interstitial fibrosis. It causes shortness of breath, and, along with mesothelioma and lung cancer, is one of the three most frequent causes of death and disease among people with heavy asbestos exposure.