THE NONMETALLIC MINERALS. 303 



The Italian asbestos which iinds it way to the Ainerican markets 

 is ))otli of the aniphiholie and serpentinous varieties, both beino- remark- 

 able for the beautiful long- fibers they yield. The amphibolic variety, 

 the true asbestos, from Mont Cenis, is shown in Specimen No. 53164, 

 U.S.N.M., and the serpentinous variety, from Aosta, in the sample, 

 No. 53161, IT.S.N.M. Both are in the form of tibrous aggregates over 

 a metre in length. 



MefhcxU of mlmng aitd preparation.— T\iq mining of asbestos is 

 carried on almost wholly from open cuts and shallow tunnels. Rarely 

 does it pay to follow the material to any great depth. In the United 

 States the mines are worked very irregularly, and in most cases aban- 

 doned at the end of a short season. 



The mining of the Canadian material is carried on by means of open 

 cuts, much as a farmer cuts down a stack of hay or straw, or by open 

 quarry on a level. The rock is blasted out and the asbestos separated 

 from the inclosing rock by a process known as "cobbing," and which 

 consists in breaking away the fibrous material from the walls of the 

 vein or from other foreign ingredients by means of hammers. 



The cobbed material is separated into grades, according to quality, 

 which depends upon the length, fineness, and flexibility of the fiber. 

 During 1888 the finest grades brought prices varying from $80 to $110 

 a ton. In 1899 the price had fallen to about $26 a ton. 



Uses.—ThQ uses of asbestos are manifold, and ever on the increase. 

 Among the ancient Greeks it was customary to wrap the bodies of 

 those to be burned in asbestos cloth, that their ashes might be kept 

 intact. In the eighth century Charlemagne is said to have used an 

 asbestos tablecloth, which, when the feast was over, he would throw 

 into the fire, after a time withdrawing it cleaned but unharmed, greatly 

 to the entertainment of his guests. The most striking use to which 

 the material is put is the manufacture of fireproof cloths for theater 

 curtains, for suits of firemen and others liable to exposure to great 

 heat. It is also used for packing pistons, closing joints in cylinder 

 heads, and other fittings where heat, either dry or from steam and hot 

 water, would shortly destroy a less durable substance. For this pur- 

 pose it is used in the form' of a yarn, or as millboard. The lower 

 grades, in which the fibers are short or brittle, are made into a felt 

 which, on account of its nonconducting powers, is utilized in covering 

 steam boilers. It is also ground and made into cements and paints, 

 the cement being used as a nonconductor on boilers, and the paint to 

 render wooden structures less susceptible to fire. In the chemical 

 laboratory the finely fibered, thoroughly purified asbestos forms an 

 indispensable filtering medium. For this purpose the true asbestos is 

 preferable to the fibrous serpentine.^ Examples of the manufactured 

 products mentioned are exhibited with the crude products. 



' Prof. A. H. Chester: Some Misconceptions Concerning Asbestos. Engineering and 

 Mining Journal, LV, 1893, p. 531. 



