The U.S. Geological Survey explains that the term asbestos is general and refers to a group of six different naturally occurring minerals. Although several varieties exist, all share some basic properties. First, they all occur as bundles of fibers which can easily separate into thinner fibers. They also exhibit a high tensile strength, possess high length to diameter ratios and are flexible enough to be spun. They also resemble organic fibers like cellulose, are incombustible and provide strong thermal stability. In addition, these minerals all possess a natural resistance to biodegradation, chemical breakdown and electrical currents.   

Groups

These minerals can further be divided into two distinct groups, which are amphiboles and serpentines. Amphiboles are found widely across the earth’s crust and make up the vast majority of all asbestos produced. These minerals, with fibers which exhibit a needle-like structure and are generally more brittle, include the following forms:

• Anthophyllite: This form of asbestos has brittle white fibers made of crystals with a chain-like appearance. It is formed by the breakdown of talc in ultramafic rock and is generally not commercially used. Nevertheless, the fibers may be found among other natural minerals which do have commercial value, such as vermiculite, which was a major component of Zonolite insulation, produced by the W. R. Grace Company.
• Amosite or Grunerite: This amphibole possesses straight brittle fibers and is commonly referred to as “brown asbestos” because its fibers range from light gray to brown in color. Once used in insulation materials, behind chrysotile asbestos, it was one of the more common varieties used for commercial purposes. Its use has since been banned in most countries.
• Crocidolite or Riebeckite: Also known as “blue asbestos,” this form can be identified by its straight blue fibers. Believed to be the most dangerous form of asbestos, it is naturally found in deposits of South Africa, though it can also be found in Australia, Bolivia, Canada, and the former Soviet Union. It is no longer produced.  
• Tremolite: Deposits of this form of asbestos are commonly found in metamorphic rocks of India, Italy, Korea, Pakistan and South Africa. The mineral’s color ranges from creamy white to dark green. Though not used as extensively as chrysotile, it has proven useful in industrial use and has also been found in household products, such as talcum powder.
• Actinolite: This form of asbestos is usually green, gray or white and can be found in deposits in South Africa and Taiwan. It is a common mineral in metamorphic rocks and is closely related to tremolite asbestos, though it possesses more iron. It was not heavily used commercially or industrially.

Serpentine asbestos is far less common and includes only the chrysotile form. This kind of asbestos possesses curly fibers, as opposed to the need-like ones of amphiboles. This has been by far the most popular form of asbestos, due to its higher flexibility, accounting for the majority of all commercial asbestos use. Below are the characteristics of chrysotile asbestos.  

• Chrysotile: Also known as “white asbestos,” the vast majority of all consumer and industrial products were manufactured with chrysotile. It consists of very fine and flexible white fibers and can be found naturally in Russia, Canada, China, Brazil, Kazakhstan and Zimbabwe. Due to its wide use, this form accounts for the majority of asbestos-related illnesses and deaths around the world.