«68 



Report of the State Geologist. 



This structure alone, however, would not suffice to give to the material 

 its valuable properties; indeed, it is not an inherent property of talc but, 

 instead, is a product of its mode of formation. The value of the talc follows 

 from its complex origin, in virtue of which it combines the fibrous structure 

 resulting from its derivation from the other silicates with its own pliability 

 and softness. The value of either mineral in its typical form would be 

 much less than that of the material which combines some of the properties 

 of both. 



Tremolite and enstatite, although fibrous, would, on account of their 

 1 (littleness, grind to a granular powder with no binding properties; and 

 the same would be true, though perhaps to a less degree, of massive or 

 foliated talc. 



In the district under consideration the terms " massive " and " foliated " 

 are often applied to varieties of talc in which the fibrous structure, although 

 present, is so fine as to be inconspicuous, except under the microscope. In 

 such cases, the character of the ground material is the same as of that pro- 

 duced from the coarsely fibrous talc; although sufficient talc that is truly 

 massive or foliated may sometimes be present to render the grinding more 

 difficult and the finished product of less value. 



The presence of scales of talc, in many specimens, indicates that it can 

 not be regarded as entirely pseudomorphous, as these scales certainly do not 

 have the form of the original minerals. On the contrary, the form is that of 

 talc itself and must have resulted directly from the independent growth of 

 that mineral. The materials, doubtless, were supplied by the constituents of 

 the schist, but the structure of the latter, physical as well as chemical, has 

 broken down. From this, it seems possible that the fibrous structure of the 

 deposits may be an indication of a lack of completeness in the process of 

 alteration which, if continued to its ultimate end, would convert all of the 

 schist to scaly talc. From what has been said above, it is evident that the 

 possibility of such a complete change of structure has an economic bearing, as 

 it would result in the destruction of the most valuable properties of the talc. 

 From this point of view the question is two-fold, involving the possibility of 

 such a complete change, and the probability of its taking place at moderate 

 depths, so as to put a stop to profitable mining. On neither of these points 

 are there conclusive data at hand but, w hile it is not impossible that such a 

 complete alteration may have occurred in some portions of the deposits, it 

 would, doubtless, be very irregularly distributed; and as it would be inde- 

 pendent of the present topography, would be developed, at such depths as to 



