Reécamination of American Minerals. 213 
an analysis made by one of us, published in Dana’s Mineralogy, 
page 692. In this analysis referred to, 3:35 per eent. of alumina 
and iron were obtained; we have since examined the relative 
proportions of these substances, and find that the amount was 
due to iron with but a trace of alumina. Two analyses, made 
from very pure specimens, gave: 
. “1 ; 
1 * Mg Fe Ni Ht 
1, 41°60 trace 4111 8°24 0:50 12 7C==299'15 
2 42°60 trace 41°90 1-62 0°40 12°70 = 99-22 
Ic is evident from these analyses that the mineral is identical 
With serpentine, and affords the same formula as the mineral last 
mentioned. It may be well to remark that great care was taken 
to see that no magnesia accompanied the oxyd of iron in its pre- 
cipitation by ammonia; not satisfied with adding an excess of 
sal-ammoniac to the solution before the addition of the ammonia, 
we re-dissolved the precipitate. added sal-ammoniac, and re-pre- 
Cipitated the oxyd of iron: this was done even a third time, be- 
fore the last traces of magnesia were got rid of, or that we were 
sure that the amount of iron would not be increased by contains 
Ing Magnesia—a circumstance in which sufficient precaution is 
hot always used. What is here said of oxyd of iron is equally 
true of alumina. 
8. Laneasterite } a mechanical mixture of Brucite and Hydro- 
magnesite. 
While on a mineral ogical excursion to the localities near Texas, 
Pa., a few months since, in company with Mr. W. W. ies, we 
ved at Wood’s Mine a peculiar magnesian mineral, some- 
What resembling Lancasterite ; a chemical examination showed 
It to be hydro-magnesite. The composition of it, as well as its 
strong resemblance to some specimens of Lancasterite, led to a 
Laneasterite is described as occurring “ foliated like Brucite,” 
but Sometimes in crystals “resembling somewhat stilbite or gyp- 
stm.” As we desired to see whether these forms were identical 
10 chemical composition, a portion of the foliated mineral was 
“welully selected, aud the amount of carbonic acid determined— 
t was but a trace: the magnesia and water being estimated gave 
same amount as is found in Brucite ; there wasalso a trace of 
Manganese and j 
s tory,) we are aware he found great difficulty in obtaining 
> Seaizs, Vol. XV, No. 44.—March, 1853. 28 
