Amosite asbestos is a form of asbestos known to cause mesothelioma. Amosite asbestos is an amphibole. The crystals vary and can be found as flat prisms, brittle grains, or long thin threads. The threads often are found in naturally occurring bundles. The long thin fibers of amosite are somewhat flexible and bend to form wide arches. These long arches of amosite fibers break into smaller groups that result in sharp needlelike fibers. The ends of the fibers are flat and do not have frayed or split ends, a characteristic that helps distinguish amosite from chrysotile. Broken bundles also are frequently found and resemble broom tails in appearance. Fragments of the crystal fibers can be identified in some building materials that were manufactured with amosite.

Amosite asbestos was used less frequently in manufacturing plants in the United States than chrysotile asbestos. South African mines were the source of most of the amosite used in the United States. This type of asbestos was named "amosite" as a description of the source of the ore, "asbestos mines of South Africa".