176 Geology of Richniond Covnfy. N. Y. 



probably long before the glacial ei)ocli ; we are only sure that 

 they are more modern than the magnesian rocks which they 

 rest upon, and older than the glacial drift, which overlies 

 them in some places. 



These beds of iron ore are found resting directly upon the 

 serpentine or talcose rocks at a number of places ; and where 

 mining has been carried on, the localities are indicated on the 

 maj?. All the deposits have the same general characteristics, — 

 they are superficial, although sometimes covered by glacial 

 drift to a variable de})th. The ore consists of the hydrated ses- 

 quioxide of iron, Limonite, and is either compact or quite earthy 

 in texture. All that I have examined gave a yellowish-brown 

 streak ; it is jiossible that there is some Hematite occurring 

 with it, but I have never seen any ore from Staten Island which 

 would give a red streak. The Limonite is associated with color- 

 less, green, and red quartz ; it has been extensively mined near 

 Four Corners, at several places on Todt Hill and Richmond 

 'JVrrace, and along the Clove Eoad, and is known to occur at 

 other places on the serpentine hills. 



The following analyses have been kindly furnished me by 

 Mr. D. J. Tysen, Jr., who is interested in the mining industry. 



(1) Ore from Todt Hill— 



Fe„ 0, 

 Mg 

 Ca 



Al, 0„ 



r ' 



Mn 

 8i 0„ 

 H.O 

 Cr 

 Metallic iron. 



The amount of Chromium is probably too high. 



67.50 per 



cent, 



1.90 





1.46 





0.82 





0.046 





1.619 





10.80 





7.73 





3.00 





47.25 per 



cent. 



