L02 



NEW YORK STATE MUSEUM 



two latter rocks being at times somewhat garnetiferous. The writer 

 is fully convinced that this transition zone (wall rock) has been 

 formed by assimilation or actual melting or fusing together of 

 the syenite and the border of the great inclusion at the time of 

 the intrusion. 



TABLE SHOWING THE MINERALOGICAL C0MP05ITI3N OF THE MATRIX OF THE GARNET-BEARING ROCK 



IN THE ROGERS AND HOOPER MINES 1 



^ Plagioclase 



Rogers mine . 



Hooper mine. 





1 













O " 



I 



20 



2 



30 



3 



50 



4 



42 



5 



30 



6 



40 



Lab. 20 



01. -an. 30 



And. 25 



01. -and. 20 



01. -and. 35 



01. -and. 20 



[il 



'is 



1 





o 



<v 



S 



^-Q 



O 



5 



H- 1 



s-= 





«< 





40 



3 



IS 



I 



I 







36 







I 



2 



little 



I 



24 









I 



little 





30 



S 



2 





i 







33 



i 



i 



I 









35 





4 



I 









little 



^A close approximation to percentage by volume only is intended. 



As shown in the field, in hand specimens, and in thin-sections the 

 garnet rock (Nos. 4, 5, and 6 of the table) at the Hooper mine is 

 almost exactly like the wall or transition rock of the Rogers mine, 

 and it also appears to grade into the country rock. In each case the 

 garnets never show reaction rims of hornblende and the garnets 

 often show good crystal outlines. In the Hooper mine this tran- 

 sition or intermediate rock makes up practically the whole mass 

 which is mined and is thus much more extensive than at the 

 Hogers mine. All evidence points to the origin of the Hooper 

 mine rock as due to rather thorough melting of an admixture 

 of syenite and Grenville sediment where the Grenville inclusion 

 was perhaps deeper down in the magma and hence subjected to 

 much greater heat, or possibly a number of smaller hornblende 

 gneiss inclusions, perhaps with some limestone, were assimilated 

 by the molten syenite. 



BIBLIOGRAPHY 

 Merrill, F. J. H. Mineral Resources of New York. N. Y. State Mus. Bui. 



IS- 1895 



Kemp, J. F. and Newland, D. H. 17th An. Rep. N. Y. State Geo!., pages 



548-49. 1897. 

 Hooper, F. C. The American Garnet Industry. Mineral Industry, v. 6. 



1897 

 Magnus, H. C. Abrasives of New York State. N. Y. State GeoL, 23d An. 



Rep. 1904 

 Newland, D. H. Mining and Quarry Industry of New York State. N. Y. 

 State Mus. Bui. 102, pages 70-73, and later annual reports on the 

 mines and quarries of the State. 1906 



