MAGNETITE IRON DEPOSITS OF SOUTHEASTERN NEW YORK 121 
The deposit is quite similar to that of the Croton magnetic mines 
in origin, habit, distribution of the magnetite, association and com- 
position. It is probable, however, that undesirable structural con- 
ditions may more or less seriously affect the ore body. 
Isolated Deposits in Putnam County 
The Tilly Foster mine. All that remains of this famous old 
mine is an extremely large brush-grown dump and a pond almost 
600 feet long and about 400 feet wide, which occupies the open cut, 
stated to be more than 600 feet deep. 
This mine once held a leading place among the magnetite mines of 
southeastern New York, contributing about 700,000 tons of ore from 
1864 to 1897. The maximum monthly production was reached in 
1879, at 7000 tons a month. The mine was first operated through a 
shaft and underground drifts; later the cover was removed and the 
mine was operated as an open pit excavation. So many serious acci- 
dents and fatalities occurred through rock falls that operation was 
discontinued in 1897; at that time a depth of 600 feet was reached. 
Mather **’ mentioned this occurrence in his report of 1839, but 
it was not until the publication of Wendt’s*” paper in 1884 that an 
adequate description of the mine appeared, although Breiden- 
baugh*” first described the rare and unusual minerals associated 
with the ore, which were called to his attention by Prof. O. D. Allen, 
of the Sheffield Scientific School, the year previous. 
Wendt (op. cit.) did not speculate on the origin of the ore, though 
he stated that the Tilly Foster and the Mahopac mines “are quite 
exceptional in their nature. In fact they are the only ones of their 
kind in the Appalachian range, if not in the world.” He described 
the fault which cut the Tilly Foster ore body diagonally, and which 
displaced it about 90 feet (see fig. 12 reproduced from Wendt’s 
paper), and he remarked on the similarity of the Tilly Foster and 
the Mahopac deposits, and the wholly dissimilar character of the 
Croton magnetic mines as compared with the two former. 
Two years later Ruttman’’* presented a very careful and pains- 
taking study of the structural features of the deposit; his paper is 
M0 Mather, W. W. 3d Annual Rep’t on the Geology of the First Geo- 
logical District, N. Y., 1830. 
171 Wendt, A. F. The Iron Mines of Putnam County, N. Y. Trans. A. I. 
M. E. 13:478-88. 1884-85. 
172 Breidenbaugh, E. S. On the Minerals Found at the Tilly Foster Mine, 
N. Y. Amer. Jour. Sci. 3d ser. 16:207-13. 1873. 
13 Ruttman, F. S. Notes on the Geology of the Tilly Foster Ore-body, 
Putnam County, N. Y. Trans. A. I. M. E. 15: 79-90. 1886-87. 
