26 NEW YORK STATE MUSEUM 



EMERY 



The mining of emery has been carried on for a number of years 

 near Peekskill, Westchester county, one of the few places in this 

 country where the material is known to occur in quantity. The 

 industry is small, as the native emery does not find so wide a market 

 as the Grecian and Turkish product which can be imported at a 

 low cost. The increasing use of artificial abrasives, also, has 

 probably restricted the output of late years. 



The Peekskill emery is a mixture of corundum, spinel and mag- 

 netite chiefly, though the mineral composition is rather variable. 

 The corundum, which of course is the most valuable abrasive con- 

 stituent, may constitute as much as 50 per cent of the entire rock 

 and in the typical material is often seen in the form of large por- 

 phyritic crystals scattered through a fine-grained mass of magnetite 

 and spinel. The rock is dense and hard, of dark gray to nearly 

 black color, sometimes mottled by the lighter color of the corundum. 

 It occurs as lenticular and banded masses within local intrusions of 

 basic gabbroic rocks which are known as the Cortlandt series. The 

 emery masses are believed to represent segregations of the heavier 

 minerals of the gabbros while the latter were in a molten condition, 

 a process similar to that which led to the formation of the titan- 

 iferous magnetites in the anorthosites and gabbros of the Adiron- 

 dacks. Some of the deposits in Westchester county contain a fairly 

 high percentage of magnetite and were once mined for iron ore, 

 but owing to the high alumina content proved too refractory for 

 furnace use. 



.Reports from the industry for the last year showed a product 

 amounting to 978 short tons with a value of $11,736. The output 

 v/as a little larger than in 1909 when a total of 892 short tons valued 

 at $10,780 was reported and considerably more than in 1908, but 

 still did not reach the level of some of the earlier years. 



The figures of production are based upon shipments, and the 

 value upon the crude rock without any treatment other than sort- 

 ing or cobbing which it receives at the mines. None of the product 

 is sold locally, but is shipped for grinding and preparation to 

 abrasive manufacturers outside of the State. The producers in 

 1910 were as follows : Blue Corundum Mining Co., Easton, Pa. ; 

 Keystone Emery Mills, Frankford, Pa. ; and the Tanite Co., 

 Stroudsburg, Pa. The Hampden Corundum Wheel Co. of Spring- 

 field, Mass. and R. Lancaster of Peekskill who were engaged in the 

 industry at one time did not make any shipments last year. 



