THE MINING AND QUARRY INDUSTRY I908 25 



are a few producers in the State who do not utilize the crude clay 

 themselves, but ship their output to others for manufacture. Some 

 of the material, like the Albany slip clay for example, is even 

 shipped to points without the State. In 1908 returns were received 

 from eight producers in this branch of the industry whose total 

 shipments amounted to 4697 short tons valued at $11,605. The cor- 

 responding total for 1907 was 3927 short tons valued at $6163, and 

 for 1906 it was 5477 short tons with a value of $9125. Besides 

 slip clay the shipments included fire clay, brick clay and the white 

 clay of Staten Island. 



EMERY 



There was a large falling off in the production of emery last 

 year, the total amounting to 690 short tons valued at $8860 as com- 

 pared with 1223 short tons valued at $13,057 in 1907. The decrease 

 in quantity was thus 533 tons and in value $4197. The output was 

 also smaller than in any recent year previously, the total for 1906 

 having been 1307 short tons valued at $13,870; for 1905, 1475 

 short tons valued at $12,452 and for 1904. 1148 short tons valued 

 at $17,220. The statistics have been based on the crude material 

 before grinding or other treatment except the rough cobbing to 

 which it was subjected at the quarries. The rock was all shipped 

 from Peekskill and distributed among the manufacturers of emery 

 wheels and other emery abrasives, whose plants are mainly located 

 in Pennsylvania. 



The list of producers in 1908 included : Blue Corundum Min- 

 ing Co., Easton, Pa. ; Keystone Emery Mills, Frankford, Pa. ; 

 Tanite Co., Stroudsburg, Pa., and J. R. Lancaster, Peekskill. The 

 total emery mined, as above given, exceeded somewhat the ship- 

 ments from Peekskill, as these amounted to 579 short tons. 



The emery is a mixture of corundum, spinel and magnetite, the 

 corundum of course being the ingredient of most value. It occurs 

 as a very hard and dense rock, of dark gray to nearly black color, 

 sometimes showing the corundum in well developed prismatic 

 cr\'stals of lighter shade. There is considerable variation in regard 

 to the mineral composition, and Magnus^ who examined thin sec- 

 tions of the material reports that in some specimens the conmdum 

 constitutes over 50 per cent of the mass, while in others it is al- 

 most wanting. The emery occurs in the form of lenses and bands 

 within an area of gabbroic intrusives known as the Cortlandt 

 series. It is to be regarded, doubtless, as a segregation of the 



'Abrasives of New York. N. Y State Geol. 23d An. Rep't. 1904. 



