GEOLOGY OF THE NORTH CREEK QUADRANGLE 79 



of a mile southeast of Holcombville (Rexford's mine) ; (3) in 

 the mixed gneiss area just south of Daggett pond (Elisha Parker 

 farm) ; (4) near the mouth of Mill creek (Sanders Brothers mine 

 now in operation) ; and (5) three-fourths of a mile east of Fuller 

 pond. Besides these the principal garnet mines of the Adirondack 

 region lie in the northern portion of the adjoining Thirteenth lake 

 sheet. One of these is the Rogers (Barton) mine near the top of 

 Gore mountain and the other is the Hooper mine on the west side 

 of Thirteenth lake. In all cases open pit methods of mining are 

 employed. 



The Oven mountain mine has not been worked for nearly twenty 

 years, and at no time was a crushing plant operated. After blasting 

 out the garnet-bearing rock and reducing it in size by means of 

 sledge hammers, the large garnets were picked out by hand. The 

 mode of occurrence is of unusual interest. The matrix, or rock 

 carrying the garnets, is a gray, medium grained, feldspar, horn- 

 blende, biotite, gneiss, a thin section showing 20 per cent ortho- 

 clase ; 25 per cent oligoclase to labradorite ; 50 per cent hornblende ; 

 2 per cent biotite ; 2 per cent magnetite ; together with a little pyrite, 

 zoisite, and apatite. Imbedded in this gray matrix are numerous, 

 well-scattered, translucent, pale reddish brown garnets ranging in 

 size up to several inches. These garnets are always quite well granu- 

 lated and never show crystal outlines. Each garnet is completely in- 

 closed within an envelop of pure, black, medium grained horn- 

 blende crystals. Occasionally a half-inch, irregular shaped crystalline 

 mass of acid plagioclase or biotite may lie just between the garnet 

 and the hornblende rim. These reddish garnets completely sur- 

 rounded by rims of black hornblende, which are in turn imbedded 

 in the gray gneiss matrix, present a very striking appearance. As 

 shown on the geologic map, this garnet-bearing rock occurs as 

 a long, narrow inclusion of Grenville gneiss within the Oven moun- 

 tain granite. 



At the Rexford mine there are several large openings but none 

 have been worked for about fifteen years. The mode of occurrence 

 is almost exactly like that in Oven mountain, only here there appear 

 to be several (smaller) inclusions of the garnet-bearing hornblende 

 gneiss instead of one, and the country rock is a very gneissoid 

 syenite. Garnets up to 5 inches across and always with hornblende 

 rims occur here. 



By way of comparison with the Oven mountain and Rexford 

 mines, the Rogers mine on Gore mountain should be mentioned as 

 of exactly the same type of occurrence but with garnets generally 



