LESLEYITE OF CHESTER COUNTY, PENN. 



AND ITS RELATIONS TO THE EPHESITE OF THE EMERY 

 FORMATION NEAR EPHESUS, ASIA MINOR. 



Several years ago a small amount of mineral from Chester 

 County, Penn., was handed to me for examination by Dr. Isaac 

 Lea, of Philadelphia. The specimen was too impure to warrant 

 any conclusion upon analysis. Its character and associates, 

 however, led me to suppose that it was the same mineral 

 described by me as associated with the emery of Asia Minor, 

 and to which I gave the name Ephesite. In the mean time 

 Dr. Lea described his mineral as a new species, calling it 

 Lesleyite; and in a recent number of the American Journal 

 of Science and Arts, S. P. Sharpies has given an analysis of it 

 that at once brought to my recollection my original opinion 

 that it was close to Ephesite, and on recurring to my examina- 

 tion of this mineral, making due allowance for the impurities 

 contained in it, the opinion was confirmed. 



I then obtained from Dr. Lea another specimen of his min- 

 eral, and proceeded to analyze both it and the Ephesite for 

 mutual comparison. Much labor was bestowed in selecting the 

 pure mineral from each, the greater part of a day having been 

 consumed in procuring the necessary quantity for analysis. 

 They are similar in their associations and identical in color 

 and luster and general physical properties. They are both 

 very difficult to decompose by carbonate of soda, even when 

 aided with caustic potash ; so that in both analyses the silica 

 obtained was fused a second time, and much alumina separated 

 from it. 



My original description of the mineral will be found under 

 Emery, in the American Journal of Science and Arts, 2d series, 

 vol. x, 1850, as follows: 



" It is of a pearly-white color, and lamellar in structure; cleavage difficult. 

 It scratches glass easily, and has a specific gravity of from 3.15 to 3.20^ 



