118 NEW YORK STATE MUSEUM 
Early in February 1880, the mines were again reopened, and oper- 
ated until the end of August of the same year, as the Cheever and 
Durant Iron mines. During this short period of operation 1344 
tons of ore were hoisted, chiefly from a pocket discovered by a 
drift from the third level *®. No more ore was found and the mines 
were abandoned. ‘They have not been operated since that time. 
According to Mather ** the “ vein” was traced to the southwest 
for a distance of more than 1% miles, and it is thought to continue 
and to form the deposit on which the “ Croton Magnetic Iron Ore 
mines’? were opened. These were formerly known as the Theall 
and McCollum mines; the Theall opening lies on the northeast side 
of the ridge, the McCollum on the southwest side. The two open- 
ings are about 2500 feet apart, and are now connected by a tunnel. 
The mines were first opened about 1880, and were in active operation 
for a number of years. In 1883 concentrating was attempted, and 
in 1889 experiments in magnetic concentration were under way. 
At that time the lower level of the Theall mine, at the northeast end 
of the hill, was 160 feet below the main adit tunnel, and the McCol- 
lum, at the southwest end, had been worked through a large open 
cut and a 60-foot shaft *”’; the stopes vary in width from 50 to 100 
feet. Magnetic concentrators were ultimately erected,*°* but the 
process was not well developed at that time and difficulties were 
encountered with the pyrrhotite ; moreover, such great masses of sul- 
phide were subsequently encountered as to cause the abandonment 
of the project. 
In 1912 plans were considered for reopening the mine; it was 
proposed to erect a mill of 1500 tons daily capacity using the wet 
magnetic method of concentration. Experimental tests indicated a 
product could be made averaging 64 per cent iron, with a phosphorus 
content of .03 per cent and with a minimum sulphur content of 0.30 
per cent. Although foundations were laid for the mill the plant 
was never completed. 
According to analyses given in the Tenth Census Report the iron in 
the ore ranges from 43.22 to 59.83 per cent, and the phosphorus 
from 0.035 to 0.260 per cent. The sulphur content is not given, but 
it is of course high owing to the presence of both pyrrhotite and 
- pyrite. 
160 Putnam, B. T. Tenth Census Report, 1880. 
161 Mather, W. W. 3d Annual Geol. Rep’t of the First Geological District 
of the State of New York, 18309. 
162 Smock, J. C. N. Y. State Mus. Bul. 7. 1880. 
163 Hoffman, W. H. Practical Results in the Magnetic Concentration of 
TronvOreransap Anyone 20 OO2 NT Soe 
