226 NEW TOEK STATE MUSEUM 



rocks which adjoin, or are intercalated with, the crystalline lime- 

 stone. It is found in segregated masses of varying sizes from 

 that of a pigeon's egg to a diameter of 20 feet. It is commer- 

 cially classified as .massive garnet, shell garnet and pocket gar- 

 net, the former being impure from the admixture of other miner- 

 als. The shell garnet is almost entirely pure and the most valu- 

 able for industrial purposes. ' The pocket garnet is that which 

 occurs in small segregations or incipient crystals in the gneiss. 

 This garnet is used almost exclusively in the manufacture of 

 sandpaper, or garnet-paper, as it is called, which is employed 

 extensively for abrasive purposes in the manufacture of boots 

 and shoes. It is also employed to some extent in the wood 

 manufacturing industry. For metals garnet is not as good as 

 emery, although some satisfactory results have been obtained 

 from its use on brass. It has been experimentally mixed with 

 emery in the manufacture of emery-wheels but without very 

 satisfactory results. 



Emery 



The variety of Corundum known as emery is quarried at many 

 points in Cortlandt township, Westchester county, from deposits 

 which occur in the eruptive rocks known as the ' Cortlandt series.' 

 It is used by the New York Emery Company at Peekskill. 



DlATOMACEOUS EARTH INFUSORIAL EARTH 



This material consists of hydrated silica, and is the accumu- 

 lation of the minute skeletons of microscopic forms of vegetable 

 life known as diatoms. It accumulates in the bottom of ponds 

 and lakes, and is found in recent as well as Tertiary and Cretace- 

 ous formations. While the living diatoms are found in all the 

 waters of the state, deposits of diatomaceous earth have been 

 reported from only two localities. One of these is in White 

 lake, town of Wilmurt, Herkimer county, and the other is on the 

 shore of Cold Spring Harbor, Long Island, on the property of 

 Dr. Oliver Jones. The latter is a fossil deposit in beds probably 

 of Tertiary age. The White lake deposit is the only one in use 



