May ], 1911.] 



THE INDIA RUBBER WORLD 



275 



Asbestos as a Commercial Product— II 



THE mechanical treatment of asbestos was first undertaken 

 by a Scottish company. In the following two years, other 

 concerns took up the problem. The general procedure 

 seems to have been pretty much the saiiu-. A cruslier was em- 

 ployed to break up the raw material, which was then scrce'ied. 

 The crushed rock, dropped from the screen on to a revolving table, 

 where the barren rock was 

 elimmatcd by hand picking. 

 The remaining material was 

 dried in a kiln, from which it 

 went to the rolls, to be 

 crushed fine. It was soon 

 found that what was needed 

 was an apparatus that would 

 break up the rock without de- 

 stroying the fiber. Two such 

 machines have been found suc- 

 cessful. One is called the 

 Beater, and the other the Cy- 

 clone. 



The Beater consists of a 

 shell of a boiler, containing a 

 shaft armed with knives or 

 "teeth." When the shaft is in 

 motion a churning of the mate- 

 rial within is the result. The 

 material may be fed into it 

 continually, as it discharges the 

 churned material automatically. 



The Cyclone apparatus is used the most, as it works with greater 

 speed. This apparatus is a castiron receptacle, containing two 

 shafts, one on either side, and shaped like propellers. These 

 operate in opposite directions and the commotion caused is tre- 

 mendous. The material ground up in this way is discharged 

 tlirou.ijh a suction pipe which deposits it on a vibrating rcreen. 



Prepari.ng to Build Asbestos Mill, Asiatic Ukals 



rock which contains the chrysolite will often be interrupted 

 here and there by pillars or walls of hard rock containing no 

 asbestos. The smaller concerns seek to keep down expenses 

 by leaving these in. The larger concerns, however, disregard 

 this transient economy, knowing that it will be necessary to 

 remove these pillars and walls sooner or later in order to 



deepen the excavation. The 

 smaller mmes are therefore 

 irregular in plan, while the 

 larger ones conform to a defi- 

 nite form. For example, the 

 mam pit of King Brothers' 

 mine has a fairly regular out- 

 line. In 1904 it was about 700 

 feet in length and averaged 

 about 200 feet in breadth. 

 The bottom ol the excavation 

 was not kept at one level. A 

 few years ago the maximum 

 depth of the pits was about 

 16S feet. A single 40-horse- 

 poiver cableway could, if oper- 

 ated continuously in the one 

 line of service, handle about 

 25 or 30 tons per hour. But, 

 because of their service abil- 

 ity for purposes other than re- 

 moval of spoil from the pit, it 

 is necessary or advisable to 

 have more cableways than the amount of spoil would indicate, 

 and placed at strategic points. One concern was employing sev- 

 eral years ago, eight cableways, although the material to be 

 brought to the surface was only about 50 tons per hour. 



All asbestos lands in Canada which belong to the Crown can 

 be acquired either by purchase of concession or may be occu- 



Boo-Koo-SuN Asbestos Property, Mongolia. 



Much of the asbestos picks up bits of iron and steel during 

 these processes, and this is eliminated by means of an electro 

 magnet. This magnet is placed sometimes at the external end 

 of the discharge pipe or sometimes over the vibrating screens. 



In quarrying asbestos bearing rock, the methods of the larger 

 and smaller concerns still differ somewhat. The serpentine 



Rich .Asbestos Property, Miass District, Asiatic Urals. 



pied and worked under a mining license. .Any person may pros- 

 pect without a license, however. 



The mines of Canada to-day produce the major portion of the 

 asbestos used in the industrial world. But for six decades or 

 more, it was known that Canada possessed this mineral, but 

 the fact was not considered of commercial importance. 



