Notes on Asbestus. 101 



varying greatly in width, appears to be a still later product 

 of alteration. In many places the serpentine contains mag- 

 netic iron disseminated in fine particles ; the associated 

 asbestus shows the same iron, not disseminated, but usually 

 concentrated toward theYmiddle of the veins. It seems 

 evident that both the serpentine and iron oxide have been 

 dissolved by percolating water and redeposited in the 

 crevices of the rock, the less soluble silicate first and lastly 

 and in the middle of the vein, the more soluble iron. 



Asbestus or chrysotile is commonly regarded as a fibrous 

 variety of serpentine, and undoubtedly the two are very simi- 

 lar in composition. Dr. T. S terry Hunt 1 has pointed out that 

 asbestus is distinguished from serpentine by its lower speci- 

 fic gravity. There are, however, other points in which it 

 appears that asbestus differs from ordinary serpentine. As 

 a rule the former contains a higher percentage of water. 

 The average water in five samples of Canadian serpentine 

 chosen at random was found to be 13.49 per cent., while for 

 four samples of chrysotile the water averaged 14.25 per cent. 

 Alumina appears to be more frequently present in asbestus 

 than in serpentine. In this respect, and in the degree of 

 hydration, Italian asbestus is similar to its Canadian rival, 

 but a greater number of analyses must be made before much 

 stress can be laid upon the presence of alumina in chryso- 

 tile. 



A question of interest, and one of great practical im- 

 portance to those engaged in the asbestus industry, is, as to 

 the cause of the difference in texture of various veins of the 

 mineral. In some cases we find the fibres very soft and pos- 

 sessed of great flexibility ; in other cases they are extremely 

 harsh and brittle, the latter being of course much less valu- 

 able than the former. Analysis shows that harsh and brittle 

 asbestus contains less water than the softer kind. The 

 writer found 14.05 per cent, of water in very flexible fibre, 

 whilst in a harsh-fibred sample only 12.62 per cent, was 

 present. It is well known that if soft fibres be heated to a 



1 Mineral Physiology and Physiography, p. 324, s. 59. 



