Rncs — Geology ok Orange County. 



423 



A drift was run in at the foot of the east slope of the hill for drainage 

 purposes. Both the hanging and foot-wall of the ore-body are of hornblendic 

 gneiss, outside of which is the normal gneiss. The ore is very lean, and 

 has a considerable admixture of quartz. No faults or dykes were observed. 

 A sectional drawing of the ore-bed is here given. 



A section of the hornblendic wall-rock shows it to be a mixture of green 

 hornblende and some plagioclase. Much of the latter is kaolinized. The 

 hornblende individuals are much bent and broken. 



The sections of the normal gneiss show a mixture of quartz and 

 plagioclase feldspar, with little or no mica. The cleavage and other cracks 

 of the feldspar are beautifully coated with limonite. Magnetite occurs 

 sparingly in grains. Fine microperthitic intergrowths were not uncommon. 



At the eastern base of Bull hill, near the south end, the gneiss presents 

 the appearance of being broken by a step-fault, the rock forming a gentle 



NW 



Figure 8. Section of Bull Hill, northwest of Monroe; showing iron mine and drift intersecting the 



ore-body. 



G., Pre-Cambrian gneiss; H., Hornblendic wall-rock; H. R., Hudson river slates; C, Cambrian 



limestone. 



slope on the west side of the wood-road, and a. perpendicular one on the cast 

 side, which slopes gently to the east on its other side. 



The Hudson river slates pass between Bull hill and the next gneiss 

 knob to the northeast. 



The road north of Rainier hill passes between two knobs of gneiss. 

 The latter outcrops on both sides of the road (-288). It is massive, and gives 

 no good dips, but the strike is about northeast and southwest. The slate, 

 no doubt, formerly extended through this cut, but it has been removed by 

 erosion, and is not met with up to a point about 300 feet east of the brook 

 west of the hill. To the north and south of the road, the slates extend some 



