REPORT OF THE DIRECTOR AND STATE GEOLOGIST 1900 r49 



may be orthoclase. Quartz is absent except as small inclusions 

 in the feldspar. The dark minerals constitute some 4:0^ of the 

 rock. The west end of the cut shows a red, granitic gneiss. This 

 shows a sharp boundary against the other, but the junction is 

 parallel to the vertical foliation of both, and a thin pegmatite 

 band intervenes. The green gneiss passes into an amphibolite 

 gneiss near the Ji;nction, but this seems clearly a phase of the 

 green, just as the pegmatite seems clearly a phase of the granite. 

 The pegmatite streak sends out stringers into the amphibolite 

 however and clearly cuts it intrusively. 



Less than i mile beyond is another long cut (1004) exhibiting 

 an identical rock assemblage. Here again the green gneiss 

 becomes black near the junction through increased amount of 

 dark silicates, but the pegmatite is lacking, the granitic gneiss 

 becomes distinctly finer grained near the contact and unmistak- 

 ably cuts the green, sending numerous thin sheets into it along 

 the foliation planes. 



Just east of the Piercefield depot, 3 f miles from Tupper lake, 

 are exposures in the bed of a brook (1005) of a green, very 

 granular, shotlike gneiss, which readily crumbles on exposure. 

 A precisely similar rock shows along the road from the depot to 

 the village (997), associated with a very rusty, rotted amphibolite. 

 Basic minerals make fully one third of the green gneiss^ hypere- 

 thene predominating, then come angite, hornblende, much less, 

 abundant magnetite and apatite and a little zircon. The remain- 

 der of the rock is feldspar, no quartz appearing. The feldspar 

 is nearly all plagioclase with 8° maximum extinction, and close 

 to oligoclase therefore. A few somewhat larger individuals are 

 of microperthlte. The rock is therefore quite like the green 

 gneiss of the preceding cuts and differs from the syenite in the 

 character of the feldspar. 



Coming into the towm, a mile from the depot, repeated ledges 

 appear of red, granular gneiss (998), composed of magnetite 

 (mnch and idiomorphic), titanite (much, of the orange, pleochroic 

 variety), augite (emerald green, pleochroic and somewhat less 

 than the titanite in amount) feldspar and quartz. The feldspar 



