April- 1, 1911.] 



THE INDIA RUBBER WORLD 



235 



Asbestos as a Commercial Product— I 



ASBESTOS, from the Greek word meaning "inconsumable," 

 is the name applied to two fibrous nnnerals, (iiii[<liibole 

 or hornblende asbestos and flirysoliU' or serpentine asbes- 

 tos. These minerals are nnich alike in external appearance, 

 chemical composition and ability to resist heat. There arc many 

 other fibrous like minerals called asbestos but none of commer- 

 cial importance. 



Ki.- 



Duu 



A^HKSTUS Ml.VE, THETIcmi), C.\N.\D.\. 



Asbestos, using the term generally, is quite widely distributed 

 over the earth's surface. It was tirst discovered in -Susa, Italy, 

 where it has been mined for several hundred years. It is also 

 found in parts of Russia, Siberia, New South Wales, Africa, 

 Mongolia, Queensland and Kngland. In our own country it is 

 confined to parts of Virginia, South Carolina, Arizona, Vermont 

 and Canada. The greater part of the world's supply comes from 

 the last named country, and is the form of asbestos known as 

 chrysotile. Chrysotile or serpentine asbestos is found in the 

 non-fibrous mother rock in tlic form of small veins, "laces" or 

 "stringers." In its original position it lies perpendicular to the 

 bordering planes. Its filler is uniform in length, very flexible and 

 clastic, and fine. The length, the controlling clement in grading 

 the various qualities, rarely exceeds two inches and is more 

 often one inch or less. 



The high temperature of 2,000 degrees and 3,000 degrees Fahren^ 

 heit it easily w-ithstands, and often a temperat\n-e ol 5,000 degrees 

 Fahrenheit seems to work no visible ill effect. Its hardness i 

 equal or somewhat superior to calcspar. In specific gravity il 

 resembles porcelain and glass, and it resists acids exceedingly 

 well. In color the Canadian chrysotile is yellow, greenish-yellow 

 and bright green to very dark green, and some blue lias been 

 found. When the fiber has been drawn out, it assumes a silk\ 

 white appearance. Typical Canadian asbestos has a chemical 

 constitution about as follows: silica, 40; magnesia. 41.3; ferrous 

 oxide, 2.5 ; alumina, 2.2, and water, 14. 



The difference between harsh and soft asbestos is largely 

 a question of the amount of water present — the more water, the 

 softer the material. Thus, it is said that a very fine quality of 

 fiber disclosed, upon analysis, the presence of 14.38 per cent, of 

 water, and a harsh specimen was found to contain only 11.70 

 per cent. Further it was observed that asbestos became brittle 

 with the expulsion of water by heat. 



The principal localities whence Canada derives her great out- 

 put of asbestos are in the province of Quebec, more particularly 

 in the eastern townships. The most important district is in the 

 vicinitv of Thetford and Black Lake. In this region are masses 



of serpentine rock intermingled with strata of slate, schist and 

 diorite. In the innnediate neighl)orhood of Ulack Lake, the ser- 

 pentine forms a mountainous ridge rising to a height of 900 feet 

 above the railway. On tliis ridge are some of the most produc- 

 tive of the asbestos mines. It is in the serpentine rock of this 

 general district that the chrysotile veins are located. The thick- 

 ness of the vein is, ordinarily, the length of the fiber, since the 

 latter occurs perpendicular to the faces of the enclosing rock. 

 The asbestos is usually detaclied without trouble. In some 

 cases, however, it clings stuljbornly and the separation becomes 

 a matter of difficulty. 



Most asbestos is mined on or near the surface. The first 

 • operation consists in breaking up the rock mass in which the 

 a.sbeslos veins occur. It has, as a rule, been found best to pro- 

 ceed as one would in a quarry. Underground methods are re- 

 garded as inadvisable. In mining asbestos by the quarry method, 

 one must consider futuii- possibilities, otherwise one will be 

 likely to dump the refuse near to the quarry, with the result of 

 sooner or later interfering with the prosecution of work. Pro- 

 vision must be made for the transportation of the raw- material 

 at once. Taught by previous experience, the operator constructs 

 a long tramway and.duni|is the refuse on a spot which he does 

 not expect to exploit. 



If the site for the mine l)e covered with surface soil, this is 

 removed. In the Blake Lake and Thetford district, the overly- 

 ing soil is sometimes 15 to 20 feet thick. If the open quarry 

 method is to be employed, the soil is removed in the summer 

 lime. The Bell .Vsbestos Company, of Thetford, have intro- 

 duced tlie steam shovel method for such work. 



Mining operations arc carried on by a terrace-like arrange- 

 ment. The rock is lilasted out with dynamite, containing about 



C.\N.\r)I.\.\ ClIRVSOTILE .V.SBESTOS. 



40 per cent, of nitroglycerin. Holes are drilled and dyninnite 

 cartridges 8 inches long and 1!4 inches in diameter are em- 

 ployed. The blast hides range in the neighl)orhood of 8 to 10 

 feet in depth. The expense for explosives is said to be aliout 

 three cents per ton where the rock is solid and massive. A 

 pound of dynamite will dislodge about A'/i to 5 tons of rock. 

 The spoil will naturally consist of asbestos bearing rock and 



