Sample of fibrous asbestos. Asbestos is a set of six naturally occurring silicate minerals that consist of thin fibrous crystals, with each visible fibre composed of millions of microscopic 'fibrils' that can be released by abrasion and other processes. The minerals are chrysotile, amosite, crocidolite, tremolite, anthophyllite, and actinolite. Asbestos was widely used as an insulating material from the 19th to the 20th Century. However, inhaling asbestos fibres can cause mesothelioma (cancer), lung cancer, and asbestosis. It was therefore phased out and ultimately banned in a wide number of countries by 1980s and 1990s. Many developing countries still support the use of asbestos as a building material, and mining of asbestos is ongoing, with the top producer Russia producing around one million metric tonnes in 2015.