Asbestos

Controlled Asbestos Mineral
Asbestos is a group of naturally occurring minerals that have a fibrous form. There are basically five (six if Actinolite and Tremolite are counted separately) natural fibers that are specified as "Asbestos" in Federal Regulations.

Chrysotile is the most common of all the asbestos minerals. It is also the least hazardous.
Amosite is the next most common of all the asbestos minerals. It was used extensively, often with Chrysotile, for boiler and acoustic insulation.
Crocidolite is the blue asbestos. It made the blue ceramic water pipe blue. It also was used for boiler insulation.
Anthophyllite, Actinolite, and Tremolite are the least common commercial asbestos minerals. They are occasionally found as contaminants in Talc and Vermiculite.