J. L. Smith on the Emery mine of Chester, Mass. 91 
but as the analysis made out and accepted as the aie ete of 
margarite did not accord with that of emerylite, I undertook t 
reéxamine margarite, when I found that its Seenponition: had 
been erroneously determined, and that it was, in fact, the same 
mineral with emerylite, which last name has had to yield to the 
priority of date of the o 
I have a ee the rade aiette from Chester and find its com- 
position as follo 
Silica, . é : : 32-21 . 
Alumina, - - - - - 4887 
ime, - - - eh oe 2602 
Oxyd of iron, - - - - 250 
Manganese, - - - - "20 
Magnesia, - - - - 32 
Soda and little potash, . - 191 
Lithia, - - - - - 32 
There is a little titanic acid with ae oxyd of iron that I did 
not estimate. 
Chlorite.—This mineral as found with the emery is the so- 
called corundophilite of Shepard; on examination it proves to 
be, Bibs chemically and physically, a chlorite of the variety 
ripidolite. 
Biotite—In examining a specimen of dark green micaceous 
mineral which I took to be chlorite (the corundophilite of 
This mineral occurs on the surface of a white rock that Prof 
Shepard vals indianite, "but which I have not had time to ex- 
amine. It is in small thin micaceous crystals perpendicular 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 pinch: 
bago. A careful analysis peli the 7 ie eympostt ion: 
Silica, - 2 39°08 
Aaa - - - - 15°38 
Magne : - . 23°58 
Phctieya of fie - - - - 712 
ea - - : “31 
Potash, - - - - 7°50 
Soda, - - . - - 2°63 
Waite « S210 - - . 2°24 
Fluorine, - . - - “76 
98°60 60 
This corresponds with the composition of the biotite from Mom 
roe county, New York, as made out by Prof. Brush and myself 
in our reéxamination of American minerals several years ago. 
