MAGNETITE IRON DEPOSITS OF SOUTHEASTERN NEW YORK 117 
yellowish green in the hand specimen, and amphibolite and chlorite 
rock, all more or less abnormal products of contact type. 
The hanging wall of the slope referred to above is essentially a 
product of contact action. It consists in places of slightly pinkish 
garnet in small grains, a granular green pyroxene colorless in thin 
section, resembling coccolite; wernerite, full of characteristic inclu- 
sions, epidote, zoisite and quartz, all typical contact products, and 
evidently the result of the complete silication of a lens or layer of 
interbedded limestone, since the ore deposit occurs in the gneiss and 
not in the crystalline limestone in the valley (see plate 14, figure 4). 
Moreover, this phase of the hanging wall is badly swamped in and 
intruded by a white, moderately fine textured syenitic aplite which 
is judged to be related to the syenitic facies of the Pochuck; the 
feldspar is moderately acid plagioclase. The footwall of the slope 
is strongly foliated, hornblendic and granitized Pochuck-Grenville. 
It seems probable that the ore body in this mine originated by the 
magmatic end-stage replacement of an interbedded limestone lens 
or highly calcareous layer in the original Grenville, and hence this 
bedy likewise belongs to the “ contact-replacement ”’ type. 
There is no record of the exhaustion of the mine, and it is reason- 
able to assume that considerable ore may be still left untouched ; 
especially in view of the geologic relations briefly outlined above. 
The chief objection to the ore is the high sulphur content, but in 
the past this seems not to have prevented the manufacture of iron 
from it. 
The Brewster belt. Beginning in the city of Brewster a belt 
extends in a southwesterly direction for a distance of about 5 miles, 
along which several mines were opened many years ago. ‘Two of 
these mines were at one time in active operation and from them a 
very considerable tonnage of magnetite has been shipped. 
The northernmost mines on this belt lie under the city of Brew- 
ster itself, one just back of the hotel formerly known as the 
Brewster House, the other at the base of the hill immediately west 
of the railroad station, both connected and essentially the same mine. 
These mines, called the Brewster Mines, have been abandoned 
over 40 years and no traces remain of them. They were opened in 
1810 and abandoned in 1820 after some 50,000 tons of ore had been > 
hoisted. Operations were resumed in 1845 and the mines were 
sporadically worked until 1875, when they were again abandoned.’*® 
19 Koeberlin, F. R. The Brewster Iron-bearing District of New York. 
Econ. Geol, v. iv, p. 713-54. 1900. 
