IRON ORES OF NEW YORK 



541 



covered in these counties, 24 only have been developed into 

 working mines, deserving of enumeration in this report. 



The earliest iron manufacture in the State was in Columbia 

 county, on Ancram creek, and was probably on these ores. The 

 Salisbury mines in Connecticut, properly a part of this iron-ore 

 district, were opened more than 150 years ago. The causes which 

 have operated in the Highlands have been effective here also in 

 closing many of the mines, so that, in 1888, there were but nine 

 at work, and four of them were closed during the year. The 

 aggregate output has declined from 144,878 gross tons for the 

 census year, 1879-80, to 43,000 tons in 1888. 



VI. The Limonites of Staten Island. 



The group of iron mines on Staten Island are in a superficial 

 deposit probably derived from the underlying rock in the process 

 of decomposition which has produced the serpentine of that 

 region. 



VII. The Carbonate Ores of the Hudson River. 



The mines of spathic iron ore, or carbonate ore, are in the 

 valley of the Hudson river, in Columbia county, south of the city 

 of Hudson, and in Ulster county near Napanock. The mines 

 south of Hudson are known as the Burden iron mines ; and, on 

 account of their extent and productiveness, and the comparative 

 insignificance of the Ulster county mines, they may be considered 

 as practically the whole of this group. The range in which the 

 Burden mines are opened is between one and two and a-half miles 

 east of the river, opposite Catskill, and is four miles in length, 

 from north to south. It lies partly in the town of Greenport and 

 partly in Livingston. The ore crops out in the western face and 

 near the crest of Plass Hill at the north, and in Cedar Hill and 

 Mount Thomas at the south. It is stratified, and its bed dips at 

 angles of 20° to 40° to the east. South of Mount Thomas and in 

 mine No. 2, at Burden, a synclinal fold has been mined out. The 

 thickness of the ore varies considerably, and for the greater part 

 of the distance the average is from 10 to 20 feet. In the Burden 

 mines as much as 30 feet of ore has been found ; in mine No. 2 

 and in Mount Thomas upwards of 45 feet. The underlying beds 

 are shaly and are probably of the Hudson river slate formation. 

 Above the ore there is a 'silicious conglomerate, which is sue- 



