|
Asbestos. [from the Greek Amíantos, 'asbestos, inextinguishable stone', through Latin Amiantus 'pure, undefiled']
Asbestos is a naturally occurring mineral that is found throughout the world. It is abundant in Brazil, and the variety found here is highly pure. There are more than 30 varieties, but only six are used commercially, in more than 3 thousand products.
How asbestos is formed:
It is believed that asbestos was formed during pre-historical times, secondary to the formation of the Earth's crust. At that time it was physically and chemically changed by pressure, heat and water that slowly began to infiltrate the surface of the rocks. Associated to magnesium and silica, water transformed the host rock into what is called mineral serpentinite, which crystallized in the cracks of the bedrock, forming parallel veins 1 to 40 mm long.
Some interesting facts on the use of asbestos:
Pottery and ceramic objects reinforced with asbestos were found in Finland. What we mean is that primitive man already knew about asbestos and had learned to mix it with clay to make more durable pots and other fire resistant household utensils.
Historians such as Pliny and Plutarch already talked about a substance that did not burn and was used by the Greeks and Romans to make fuses and wicks for their oil lamps. Romans and Vikings also discovered in the Europeans Alps, deposits of a "magical" mineral, that could be spun and woven into cloth.
Charlemagne, the Emperor of the Holy Roman Empire used to surprise his guests by throwing the towels covering the banquet tables into the fire and later retrieving them intact.
Marco Polo reported on the wonders that he saw during his travels through the Far East. He saw incombustible "magical cloths" in Siberia, located to the north of the Empire built by Genghis Khan. The local inhabitants "wove an indestructible cloth with a mineral that they extracted from the earth".
The first attempts at mining asbestos commercially began towards the end of the 17th Century in New France, in Canada. These deposits had been discovered while people were prospecting for copper, gold and iron.
In 1862, asbestos was presented in a public exhibition which was taking place in London. In 1883, the English journal The Engineer featured an article called Asbestos and its application by an unknown author, who discussed the use of asbestos, as lining and insulating material for the steam engine boilers that John Bell introduced to the world in 1879. These engines were later adopted by the English and German Navy.
The use of asbestos was disseminated during the 40s and the 50s in North America, Europe, Australia and Japan, as thermal insulator and fire proofing material. The material was applied with a spray gun containing asbestos fibers and dust and this process was used in metallic structures, boilers, generators, train wagons, as well as in ship and train cabins. The objective was to protect the passengers and the facilities against the effects of a possible fire. During this application workers were exposed to excessive amounts of fibers that remained suspended in the air. In the countries mentioned above, people used amphibole asbestos, which has now been banned throughout the world because it is extremely harmful to the human health.
In Brazil the use of amphibole asbestos was very restricted. The sectors that use fiber cement with asbestos, as well as brake manufacturers have always consumed around 80% of the asbestos used in Brazil, and most of the time, they use chrysotile asbestos.
|
