Not in the case of natural slate, these minerals are not compatible with it. It is understandable why some contractors are very cautious when removing any roof constructed in the last century.Īsphalt tar paper and shingles, and tiles made of mineral fiber and fiber cement, are good candidates to have asbestos on their composition, and need a special procedure for their removal. After the infamous attack of 9/11, the towers of the World Trade Center released an unknown amount of asbestos, which risked the lives of the emergency workers. This is a problem, because the health of the people using these buildings is in danger, but removing and substituting the asbestos can be even worse. However, there are still many buildings constructed during the last century with important proportions of asbestos in their materials. The public health problem grew exponentially, and by the end of the 20 th century, the use of asbestos was banned in most of the countries. The asbestos properties were attractive and useful for building purposes. One field in which asbestos were used profusely was in construction. You could find asbestos in many objects, from blankets, car brakes, even artificial snow flakes used in Christmas decoration. This did not prevent their use in new industrial applications during the 20 th century. However, by the beginning of the 20 th century, some scientific studies discovered the toxicity of these useful minerals. Asbestos have been used by mankind since prehistoric times. They are flexible and can resist high temperatures, which gives them a lot of industrial applications. But, what is the problem with asbestos? Asbestos is the name of a group of fibrous minerals, such as chrysotile (white asbestos), amosite (brown asbestos), or crocidolite (blue asbestos), among others. It is not possible to create asbestos from a pelitic sediment, as it is impossible to make an apple pie from a steak. Asbestos only form from basic and ultrabasic rocks, which are rock with a very low quartz content. This creates a rock with a characteristic cleavage that can be split and used as a roofing material… you know, the old tale we have discussed before about roofing slate origins.Īlternatively, asbestos minerals need different ingredients. If more pressure, time and temperature is applied, the mineral evolution would continue, and new ones would appear. These new minerals are mostly a recrystallization and rearrangement of the old ones, so the resulting rock (slate) has also dull, strong and hard minerals: quartz, mica and chlorite. This transformation implies the dissolution of some of the original minerals and the formation of new ones. Once this clay is buried inside the Earth, it begins its transformation into slate, due to the slow effect of the tectonic forces, which cause an increase in temperature and pressure. These type of sediments are also called pelitic sediments, from the Greek pelos (clay). Our starting material, the clay, is made of no more than quartz, mica and some chlorite, which are hard, dull and common minerals. These clays are the remains of the eroding and wearing of rocks, only the toughest minerals can survive to this cycle. In the picture: renovated roof with natural slate (left), old roof with asbestos (right).Īs you know, roofing slate is formed from clay. Roofing slates do not have asbestos, it is mineralogically, chemically and geologically impossible. There are two ways to give an answer to this concern, the short one and the long one. For a while now that I hear more and more people asking about the asbestos content of roofing slate.
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