MINERAL RESOURCES OP THE STATE OF NEW YORK 



287 



Methods of occurrence. The talc deposits consist of bands, 

 lenses and irregular masses enclosed by the Grenville limestones 

 and schists. One or both walls may be limestone; but in some 

 deposits the talc is bordered on one side by unaltered tremolite 

 schist, the line of demarcation between the two materials being 

 well defined. They are not veins, except as that name may be 

 applied to the small bodies of foliated talc that fill openings within 

 the other, but represent portions of the tremolite schist that have 

 been subjected to alteration underground through the agency prob- 

 ably of deep-seated circulations. It is certain that the talc is not 

 a product of surface v/eathering. 





s 



Gi'eiwiiiG 



LiiriG3l'orie 



Ti'-cmolitc 



Talc Granite 



Generalized section of the Edwards talc deposits 



The individual deposits conform in structural features with the 

 wall rocks, having usually a northeast-southwest trend which is 

 that of the limestones but showing minor plications and crumplings 

 and small faults seldom observable in the limestone. The dip of 

 the deposits is to the northwest at angles that usually lie between 

 30° and 60°, but which occasionally reach nearly verticality. It 

 may vary extensively in the same deposit, through the presence of 

 rolls by which the dip changes abruptly with more or less regularity, 

 and through the gradual steepening of the inclination with depth 

 which is a common experience. 



The lenticular form of deposit seems most common, though every 

 variation from the type may be found. The thickness of the deposit 

 from wall to wall seldom exceeds 30 to 40 feet, while the dimensions 



