462 J. L. Smith—Chromite from Cohahuila. 
I was at once struck with its being different from any nodule 
I had yet observed in meteoric iron. ere was no troilite in 
it; and although black it was not graphite; so that I supposed 
it might consist entirely of daubréelite. But its luster was more 
vitreous than in this last mineral. n examining carefully 
with a lens, I found in the black material a few particles of a 
translucent mineral, some particles of which were almost color- 
less, and one or two of a greenish hue (doubtless magnesian sil- 
icate) ; and, besides, there were a few specks of iron only trace- 
able by the magnet. 
The nodule was virtually a black granular mass. As stated, 
it was first taken for daubréelite. The smallest particle rub- 
bed fine and fused with borax gave the intense green of chrome ; 
but, to my surprise, when the powder was heated in nitric acid 
over a water bath, not the slightest impression was made upon 
These reactions convinced me that I had chromite; and on 
fusing 150 milligrams of the finely pulverized mineral with ten 
times its weight of bisulphate of soda, it was thoroughly 
attacked but not dissolved. On treating with water, and fusing 
the residue with carbonate of soda and niter, and proceeding 
with the analysis as is usual in the case of chromite, there was 
obtained, 
Chromic oxide 62°71—€r 
Ferrous oxide 33°83—Fe 
the iron oxide being in the solution from the fused mass, after 
treatment with bisulphate of soda. The composition thus foun 
y 
of chromite has been observed by the assistant of the Professor 
of Geology in the College of France. The name of this assist- 
ant I do not now recollect and I cannot now place my hands 
on the results of his researches in this direction. 
. 
