GEOrjHiV OF SARATOGA SINKINGS AND VICINITY 23 



through the surrounding schists. Except for being usually more 

 quartzose they are quite like the granite in mineralogy, coarsely 

 crystalline aggregates of quartz and white feldspars (microperthite 

 and oligoclase) with some biotite and often garnets. The schists 

 just to the north of Saratoga, as shown along the Adirondack Rail- 

 road and along the north margin of Highland park, are full of 

 these dikes ; and a little farther north, along the fault scarp, the 

 granite shows well and accessibly and has been quarried somewhat, 

 [n addition to the usual minerals these dikes show here and there 

 other and rarer minerals. The old chrysoberyl locality, just to the 

 north of Saratoga, is on one of these dikes in the schist. In this 

 a lot of black tourmaline has developed, so that the pegmatite is a 

 (juartz-feldspar-tourmaline-garnet rock, in which frequent nests of 

 chrysoberyl crystals occur. The dike cuts a hard mica gneiss and is 

 about 3 feet wide at the old pit. One and one-half miles south 

 of South Corinth is another old mineral pit on a pegmatite vein in 

 schists, which furnished fine black tourmaline and rose quartz. 



Mixed rock. With the exception of the pegmatites practically all 

 the granite is contaminated with schist. We interpret this con- 

 tamination as resulting from the shredding and dispersion of the 

 schist inclusions in the granite under conditions of extreme pressure 

 and metamorphism. All gradations occur between bands of schist 

 somewhat impregnated by granite and granite that seems normal 

 except for the fact that it may be somewhat more micaceous than 

 it should be. This introduces an element of uncertainty in the 

 attempt to in\estigatc the granite chemically. 



Chemical composition. The material chosen for analysis was 

 obtained from the quarry in the granite on the face of the fault 

 scarp 2 miles north of Saratoga, and was chosen because it was 

 fresh and because contamination with schist seemed slight, if any. 

 The thin section showed quartz. al)out 2^ per cent, feldspars about 

 ecjually divided between oligoclase on the one hand and microcline 

 and microperthite on the other, about 70 per cent, and the remainder 

 biotite, except for a few small zircons and a trifle of apatite and 

 titanite. The liand specimen shows occasional garnets, none of 

 which got into the tliin section. The rock shows a rude banding due 

 to variations in tlie amount of mica, suggesting a trifle of shredded 

 schist in the more micaceous bands, but not enough to imi)air 

 materiallv the value of Doctor Morlev's analvsis. 



