THE MINING AND QUARRY INDUSTRY I9II IO^ 



among the very earliest of the Adirondack formations. The 

 granite is fonnd in dikes, stringers and irregular bodies and belongs 

 probably to one or more of the great invasions of that rock which 

 took place in the Adironacks at different times in the Precambric 

 period. Both fine-grained and pegmatitic varieties occur. The 

 other important Adirondack intrusives including syenite, gabbro, dia- 

 base etc., are absent so far as known. There are no Paleozoic strata 

 though they begin a few miles to the west with horizontal beds of 

 Potsdam sandstone. They no doubt extended over this area at one 

 time and reached far into the interior of the Adirondacks, but have 

 been planed off by erosion. 



The limestones and schists have a northeasterly strike and are 

 upturned at a high angle, the dips being usually 45 ° or over toward 

 the northwest. The limestone is coarse and carries abundant 

 silicates. The latter in places constitute the greater part of the mass. 

 The tremolite schists from which the talc beds are derived repre- 

 sent the extreme stage in the silication of the limestones. The 

 quartzose schists and hornblende gneisses are probably metamor- 

 phosed products of impure sandstone and shales. 



The zinc ores at Edwards occur in a mass of impure serpentinous 

 limestone which forms a low ridge just north of the Oswegatchie 

 river on the road to Trout lake. On the north end of the ridge 

 there is a shallow open cut showing a band of mixed blende and 

 limestone about 15 feet thick. The blende occurs in irregular 

 bunches which apparently are the brecciated fragments of what was 

 once a more or less solid lens or band of the ore. There is evidence 

 of intense compression which has forced the limestone into the 

 fractures and recemented the mass. The limestone for some dis- 

 tance away from the lens is impregnated with blende so as to form 

 a lean ore. The occurrence has not been tested for any considerable 

 depth. Several other showings of ore are found on the sides and 

 top of the ridge to the south of this opening. About 1000 feet away 

 and on the opposite or eastern side of the ridge is the one which 

 has been explored during the past season, as above mentioned. In 

 this place the ore shows less evidence of compression or disturb- 

 ance and admixture with limestone. The lenses also have well- 

 defined walls. The blende is finely granular without any trace of 

 crystal form. The pyrite is sprinkled through the mass in rounded 

 grains which range up to one-fourth inch in diameter and occasion- 

 ally show a cubical development. Barite is found in some quantity 

 in the walls. On the weathered outcrop it shows prominently as a 

 spongy aggregate that was first mistaken for smithsonite. 



