68 NEW YORK STATE MUSEUM 



silica, and usually less than 2 per cent of combined iron oxids, 

 alumina and lime, the remainder being water. 



Diatomaceous earth occurs at several localities in New York 

 State, but the only deposit that has been worked of late years is 

 that near Hinckley, Herkimer co. A bed from 2 to 30 feet 

 thick forms the bottom of White Lead lake, covering an area of 

 about 4 acres. It is under 4 feet of water. The material is exca- 

 vated and purified by washing and settling in vats, after which it 

 is compressed into cakes. The main use of the earth is in the 

 manufacture of polishing powders. The single producer is George 

 W. Searles of Herkimer. An analysis shows the following chemical 

 composition : 



Silica (SiOs) 86.515 



Alumina (AI2O3) .449 



Ferric oxid (FcgOg) . 374 



Lime (CaO) . 120 



Water and volatile matter 12. 120 



Undetermined . 422 



100.000 

 In township 43, Herkimer county, there are a number of ponds 

 and lakes containing diatomaceous earth in beds of varying thick- 

 ness. A detailed description will be found in a paper read before 

 the New York Academy of Sciences by Charles F. Cox, to which 

 reference is made under the appended bibliography. In all, eight 

 localities are named by Mr Cox, the list including Roilly pond. Big 

 Crooked lake, Chub pond, Hawk lake and other smaller bodies of 

 water. An area of from i to 5 acres of the material was found in 

 each locality and soundings showed a thickness up to 20 feet or more. 

 The earth is said to be very pure. 



Bibliography 



Merrill, F. J. H. Mineral Resources of New York State. N. Y. State Mus. 



Bui. i5,p.555. 

 Cox, Charles F. N. Y. Acad. Sci. Trans. 1893. 13:98. 



EMERY 



Deposits of emery are found in Westchester county, southeast 

 of Peekskill. The mines, which were first opened for iron ore, 

 occur along the contact of basic igneous intrusions belonging to the 

 gabbro series. They are mostly shallow and ordinary quarry 

 methods are employed in extracting the material. 



