4 ANNALS NEW YORE ACADEMY OF SCIEN8E8 



Garnet 3X 15 Y OZ 2F 



Titanite OX 20 Y OZ OF 



Zircon OX 20 Y OZ OF 



Apatite OX 20 Y OZ OF 



Pyrite OX 7Y OZ 13 F 



Pyrrhotite OX 5Y OZ 15 F 



Magnetite OX 9Y OZ 11 F 



Carbonates OX OY 12 Z 8F 



Kaolin OX OY 14 Z 6F 



From this summary, we see that quartz, orthoclase, oligoclase, horn- 

 blende and biotite are the essential minerals, and that garnet, titanite, 

 zircon and apatite are the common accessories, while microcline, anortho- 

 clase, augite, pyrite, pyrrhotite and magnetite are rarer. The acid min- 

 erals are dominant. 



Granite Phase 



The hand specimen shows a medium dark gray rock, evenly and finely 

 granitoid in texture and essentially composed of quartz, feldspar, horn- 

 blende and mica. Pink garnets of small size are present throughout the 

 specimen and give it a mottled appearance. The rock is slightly gneissoid. 

 The feldspars are fresh and semi-transparent and show polysynthetic 

 twinning. The hornblende is a dark green variety, sometimes almost 

 black. 



Under the microscope, great differences in the size of grains are no- 

 ticed, and there is also a tendency for the smaller grains of quartz and 

 feldspar to surround the larger ones. The small individuals seem to be 

 the result of the crushing to which the rock was subjected. Fractures are 

 common in the rock and are coated with limonite and in some cases with 

 quartz. The following minerals have been identified in the slide : quartz, 

 orthoclase, anorthoclase and hornblende as essential minerals, also micro- 

 cline, oligoclase, garnet, titanite, apatite, zircon, augite, magnetite and 

 pyrite. Secondary alteration is slight, although limonite and kaolin are 

 noticeable. 



The quartz occurs allotriomorphically and also as small elongated 

 prisms included in the feldspars. The latter case show between crossed 

 nicols a fine rim of interference colors. Included in the quartz are zircon, 

 apatite, biotite and fine trails of dust. Some of the quartzes have deep 

 embayments and irregular outlines due to resorption. Nearly all show 

 wavy extinction. 



The predominant feldspar is orthoclase. This is, as a rule, allotrio- 

 morphic. Microperthitic structure is faintly developed. Carlsbad twins 

 are common. Cleavage parallel to (010) is well marked, not so strong 



