Six minerals are defined as “asbestos” in two different classes. In Canada only the serpentine class has been mined. The serpentine class includes only the fibrous mineral chrysotile. It is more flexible and has a wider range of uses because of that quality. Chrysotile is white. It is argued by the Canadian industry and its supporters that chrysotile or “white asbestos” is less dangerous than the minerals in the other class of asbestos known as the amphibole class. With chrysotile many of the uses tend to result in the asbestos fibers being on the inside of building materials where there is less direct exposure to the fibers for possible inhalation. The danger is less in some situations but it is not accurate to simply say chrysotile is less deadly.
The amphibole class is made up of crystal forms and includes the minerals amosite, crocidolite, tremolite, anthophyllite and actinolite. The amphibole forms are usually blue or brown. There is an important distinction to be made between serpentine and amphibole asbestos due to differences in their chemical composition. Blue asbestos is sprayed on with many uses and as such blue asbestos in such use more brittle and more likely to break off into the air for inhalation. Brown asbestos tends to be used for fireproofing boards and wall and with such use tends to be painted over or covered which reduces the danger. It is often said that blue asbestos is the most dangerous and blue asbestos is no longer mined. Asbestos in all forms of asbestos (including chrysotile asbestos) are known to be human carcinogens.