606 



Report of the State Geologist. 



the furnaces upon lake Sanford. On the road to Newcomb the same rock 

 again appears at several points and furnishes a fine bluff on the south shore of 

 lake Harris near No. 47.* Black hornblendic gneiss forms a hillock at No. 47, 

 while just across the bridge leading to lake Newcomb is a green, rather 

 massive gneiss, which under the microscope exhibits orthoclase, or at least 

 untwinned feldspar, some plagioclase, quartz and hornblende. The same rock 

 is met on the road to Mr. Pruyn's camp, in some of the borrow pits, and has 

 been noted elsewhere in the county. Crystalline limestone and its char- 

 acteristic associated black schistose and quartzose gneisses are met as far 

 west as the town line. On the road to Newcomb lake, gneisses generally dark 

 and hornblendic are seen, but on the shores of the lake at No. 131, just north of 

 Mr. Pruyn's camp, white limestone again appears, with graphite, brown tour- 

 maline and blue apatite all in small and poorly developed crystals. This 

 ledge was also a source of stock for the early furnace near lake Sanford. At 

 Watch Rock, at No. 132, on the southwest side of the lake, is a quartzose 

 gneiss, and again at No. 134, called Flat Rock point, there is a dark graphitic 

 gneiss, which is doubtless a metamorphosed sediment. 



It will be a matter of great interest to determine the geology of the 

 northwestern portion of the town, because it seems probable from the 

 character of the country, as seen from afar, that the anorthosites and gabbros 

 end with Santanoni and that this region of lakes and moderate hills will 

 prove to be gneisses and limestones. The anorthosites are of course well 

 known far to the southwest and may form isolated knobs in the region between 

 Newcomb and the line of the Adirondack and St. Lawrence railroad, and 

 they are present around the Preston ponds, but the country, so far as scattered 

 observations indicate, is mostly gneisses and limestones. Much the same is 

 likely to prove true of the southwestern corner of xhe town. 



Series III. The anorthosites and gabbros practically make up the 

 eastern third of the township. On the highway from North Hudson, gabbro 

 is met at No. 49b, just east of Tahawus. On the road from Tahawus (often 

 called the Lower Works) to the old Adirondack village (the Upper Works, or 

 "Deserted Village") strongly gneissoid rocks first appear, but near lake San- 

 ford's southern end they yield to well-developed anorthosites which form the 

 hills on each side. At the prospects on the great Sanford vein, at Nos. 43 

 and 44, the wall-rock is a massive aggregate of labradorite, and little else, and 

 from the ledges in the river and hillsides, near the present club-house, the 



* This is the locality of the fine tourmalines first brought to notice by Professor Beecher and described by Mr. F. L. Nason 

 in Bulletin New York State Museum, Vol. I., No. 4. 



