REPORT OF THE DIRECTOR I917 1 17 



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" syenite," that is more nearly allied to the granites. It is com- 

 posed of the same kind of feldspar that characterizes granites, 

 namely, orthoclase, although this is very frequently replaced by 

 " microperthite." The other chief component is either black-green 

 pyroxenes or black hornblende; quartz and mica are to a very large 

 extent lacking. The syenite rocks received their name from Syene, 

 whence came the Egyptian granite in ancient times, although these 

 two rocks do not resemble each other when compared according to 

 modern methods. The syenite of this region has a green color due 

 to the hornblende and augite it contains, which makes it easily 

 distinguishable from the grayish or dark blue of the anorthosite. 



The syenite is exhibited to the east of Lake Clear, as can be seen 

 on the accompanying map. Unfortunately, however, no exposures 

 of the typical syenite were found near Lake Clear, for most of them 

 have been affected by contact with other rocks. In the neighbor- 

 hood of Lake Loon, on the slopes of Katy mountain, syenite rocks 

 are typically developed (plate 4). One exposure occurs in the 

 town of Saranac Lake on the east side of the state road from Lake 

 Clear, just north of the two railroad crossings, that shows an abnor- 

 mal banded rock. This exposure will be more fully treated later on. 



Professor Cushing has shown by means of rock exposures farther 

 south in the vicinity of Long Lake that the syenite is of later age 

 than the anorthosite, thus establishing the time relations accepted 

 by the writer. 1 Recently the writer has verified this conclusion by 

 two exposures, one south of Mountain pond, northwest of Paul 

 Smith's, and another 2 miles west of Gabriels. 



In the southeastern Adirondack's granitic rocks occur that are 

 closely associated with the syenites and are considered to be merely 

 quartzose phases or members of the normal granite. Thus a granite 

 should be mentioned in the list of igneous rocks of the series. These, 

 granites are considered as segregations or differentiations of the 

 syenite, and hence may be termed the granite-syenite intrusives. 2 



The third member of this group of igneous rocks is the " gabbro " ; 

 a dense green-black rock somewhat similar to the anorthosite, but 

 containing more pyroxene at the expense of the labradorite. Around 

 Lake Clear the gabbro is scarce and occurs only in very small patches 

 or as a filling of cracks in the older rocks, but in the eastern portion 

 of the mountains considerable areas plentifully exhibit this third 

 and last member of the series. One small knob of gabbro is found 



1 N. Y. State Mus. Bui. 115, p. 481. 



2 William J. Miller, N. Y. State Mus. Bui. 170, 182 etc. 



