BY EDGAK HALL, F.C.S., AND HENRY G. STOKES, F.G.S. 115 



Asbestos is a mineral known slightly to everybody since 

 the introduction of gas-heating appliances, but the technical 

 knowledge necessary to form a just estimate of the value of 

 different samples seems rare even among mineralogists and 

 geologists. Asbestos is the name given by mineralogists pro- 

 perly to the fibrous variety of hornblende, but is applied generally 

 to the fine fibrous forms of many minerals whose composition 

 is essentially that of a hydrous silicate of magnesia and other 

 bases. In commerce practically the term " asbestos " is confined to 

 the mineral chrysotile which is not a variety of hornblende, but 

 is supposed to be a fibrous serpentine, and consists of a hydrated 

 silicate of magnesia of the following average composition : — 



Water . . . . . . 14-0 per cent. 



Silica . . . . . . 43-5 per cent. 



Magnesia . . . . . . 40'0 per cent. 



Other bases . . . . 2-5 per cent. 



100-0 



This mineral occurs very widely distributed throughout the 

 world, but apparently not very often in quality and quantity 

 sufficient to be of industrial value. At the present time, the 

 chief, if not the only sources of supply are Italy and Canada, 

 the latter country furnishing by far the larger quantity. 

 Italian and Canadian Asbestos agree closely in chemical 

 composition, but differ materially in physical characters and 

 in mode of occurrence, each possessing certain peculiarities 

 rendering it more suitable for certain purposes, but in the main 

 they are of equal value. The Italian is noted for its great 

 length of fibre and extreme silkiness, but it is said to be less 

 fitted for spinning than Canadian. The first manufactured 

 asbestos goods were made from Italian Asbestos, and for a 

 time it was supposed that the short fibred Canadian variety 

 could not be spun, but now the short fibres are utilised without 

 difficulty, and are said to possess more cohesion than the long 

 silky Italian fibres. As the asbestos found hitherto in Aus- 

 tralia resembles the Canadian article, the following remarks 

 apply chiefly to Canadian chrysotile : — 



Asbestos occurs in serpentine formation in irregular veins 

 from the size of minute threads up to 4, 5, and 6 inches wide. 



