J. L. Smith on the Emery mine of Chester, Mass. 87 
like the gneiss again, are strikingly free from quartz or uncom- 
bined silica in any of its forms. Indeed this generally abundant 
substance is altogether wanting, not only in the emery-vein but 
in the talcose formations constituting its eastern bounda: 
t makes its appearance, however, in abundance in the mica 
slate as soon as the taleose rocks are passed—showing itself not 
only as the usual ni a tae of the slate, but in more or less 
continuous seams, a few inches thick up to above six inches, 
and sometimes a foot, j in width. Where the seams are thin and 
discontinuous, the included masses thin out at each end beens 
a the sharp edges being curved in opposit® diree- 
tions, so as to form frequent white patches upon the surface of 
the rocks in the shape of the letter 8.” 
Mineralogical Character and Composition of the Chester Emery. 
It resembles more nearly that from Gumuchdagh — Eph- 
esus,) than any other that I know of. It is of a fine grain, and 
dark blue bordering on black, not unlike certain variate of 
magnetic iron ore; with it there are frequently found pieces of 
corundum of some size. The interior of the mass is free from 
micaceous specks, such as are found in the emery of Niles Its 
powder examined under the microscope shows the distinct exist- 
ence of more than one mineral, which are often so inseparably 
connected that the smallest fragments contain them together. 
The two predominating are corundum and magnetic oxyd of iron. 
Several s were submitted to chemical examination 
from sees most largely impregnated with Scone ince of 
iron to those that appeared to contain least. They all consisted 
essentially of alumina and oxyd of iron; aoe I invari found 
a little titanic acid and silica, and most ¢ monly a mag ute 
quantity of magnesia. No. 1 was an ceberion é specimen; No. 2, 
the better quality of rock; No. 3, the emery rock mea et and 
prepared for market in the form of emery; No.4, the same, and 
called emery crystals. 
2. ; 4. 
Alumina, 44:01 50°02 51:92 74:22 
iad oxyd of iron, 50°21 44°11 42°25 19°31 
Silic 3°13 3°25 5°46 5°48 
I examined a specimen of No. 2: grain fine, and treated re- 
peatedly with hydrochloric acid and water over a water-bath: 
great deal of oxyd of iron and a little alumina were dissolved; 
ihe residue on analysis proved to be nearly pure corundum, 
giving, 
Alumina, oS 
Magnetic ahs of iron, - - - - 9°63 
ilica,’ - - - - 81 
‘No attempt was made to estimate the water. 
