52 EMERY MINE OF CHESTER, MASS. 



Shepard) and from its purity expected to get a very accurate 

 idea of its composition, but in the very commencement of the 

 examination it was discovered to be well-characterized biotite. 

 This mineral occurs on the surface of a white rock that 

 Professor Shepard calls indianite, but which I have not had 

 time to examine. It is in small thin micaceous crystals per- 

 pendicular to the surface of the indianite; in the mass it is of 

 a dark -green color, so dark that at a little distance it looks like 

 lamellar plumbago. A careful analysis gave the following com- 

 ■ position : 



Silica 39.08 



Alumina 15.38 



Magnesia 23.58 



Peroxide of iron 7.12 



Manganese .31 



Potash 7.50 



Soda 2.63 



Water... 2.24 



Fluorine 76 



98.60 



This corresponds with the composition of the biotite from 

 Monroe County, New York, as made out by Prof. Brush and 

 myself in our re-examination of American minerals several 

 years ago. 



Corundophilite proved to be a Chlorite. — About the time I pub- 

 lished my memoirs on emery in 1850 and 1851, Prof. Shepard 

 made the announcement of a new mineral (American Journal 

 of Science and Arts, 1851, XII, p. 211), stating that it " occurs 

 with corundum near Ashville, in Buncombe County, North 

 Carolina, in imperfect stellate groups, and also spreading out 

 in laminae between the layers of corundum; color leek-green, 

 etc." An analysis afforded silica 34.76, protoxide iron 31.25, 

 alumina 8.55, water 5.47, making a loss of nearly 20 per cent., a 

 portion of which he attributes to alkalies; neither lime nor mag- 

 nesia were detected. He operated on one hundred and forty 

 milligrammes. This mineral was considered a new one, and 

 Prof. Shepard called it corundophilite. Supposing that I had 

 observed the same mineral in certain specimens of emery and 

 emerylite from Chester, Massachusetts, I inclosed a fragment 

 of the specimen to Prof. Shepard to ascertain if this was the 

 mineral he called corundophilite; he returned the specimen 

 announcing that it was. I then analyzed the same and found 



