Occurrence And Mining
The primary sources of the asbestos minerals are Quebec and the Yukon in Canada and the Ural Mountain region of Russia (chrysotile) and southern Africa (the amphiboles and amosite). Some asbestos is also found in Mexico and Italy, and in the United States, in Arizona, California, North Carolina, and Vermont.
By far the greatest amount (95%) of asbestos produced today is chrysotile. An additional 3.5% consists of crocidolite, and the final 1.5% is amosite.
The largest supplier of asbestos minerals has traditionally been Russia, or the former Soviet Union, which accounted for about half of all the asbestos mined in the world. The second largest source has been Canada (about 30% of the world's output), followed by the European nations, Zimbabwe, China, South Africa, and the United States.
Asbestos occurs either in seams that run at or just beneath the earth's surface or in veins that may go as deep as 327 yd (300 m). One method of quarrying the seams is known as block caving. In this process, trenches are dug underneath an asbestos seam and the whole section is then allowed to fall and break apart. In another technique, open seams of the mineral are plowed up and allowed to dry in air.
Underground veins are mined in much the same way as is coal. The distinctive fibrous character of asbestos makes it relatively easy to separate from other rocky material with which it is found.
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