Smyth — Talc Industry of St. Lawrence County. 



669 



prevent further working, only by a coincidence. For these reasons, it seems 

 entirely justifiable to neglect this factor in estimating the extent and value of 

 the deposits. 



In the case of most mine products, the chemical composition is the most 

 important feature, the aim being to secure the greatest amount possible of 

 one or more constituents of the material mined and in a condition suitable 

 for extraction. With the talc, this is not so; its value is entirely dependent 

 upon its physical properties, and its chemical composition is of importance 

 only as it conditions these. The connection between physical properties and 

 chemical composition is, of course, most intimate, and hence the composition 

 is of importance indirectly. The value of the material does not, however, 

 depend upon the presence of some one element which is to be extracted, but, 

 instead, upon the character resulting from the union of all the elements 

 present. 



If any one constituent can be said to have particular value, it is the 

 water. Its importance lies in the probability of its giving the soft and pliable 

 character to the mineral. Of course, it is impossible to say that this is posi- 

 tively the case, but it is a familiar fact that many minerals which contain the 

 elements of water are softer than other minerals having nearly the same com- 

 position aside from this constituent. In using the term " water " in this 

 connection it is not meant to imply anything definite as to the condition in 

 which its elements are present ; for in most cases, as with the talc itself, this 

 is a disputed point. 



The predominant importance of the physical properties of the talc ren- 

 ders simple mechanical tests of more practical value than elaborate chemical 

 analyses in determining its grade. Were the material of sufficient value to 

 demand careful discrimination in dealing with it, microscopie examination of 

 the powder would perhaps afford the most accurate method of grading. By 

 this means the perfection of fibrous structure, together with the relative 

 amounts of talc, tremolite and foreign impurities could be rapidly determined. 

 With existing prices, however, such refinements are unnecessary. 



A chemical analysis, of course, shows whether the alteration of the schist 

 into talc is complete and, if made on a sample taken from a fibrous mass, is a 

 thorough test of the value of the material. But aground sample might afford 

 an excellent analysis, and yet lack entirely the fibrous structure necessary to 

 give it the desired binding properties. In this way, a purely chemical exam- 

 ination might lead to very inaccurate conclusions as to the quality <>\ the 

 material. 



