G. J. Brush on Chalcodite. ; 201 
This composition approaches’ that given: by Rammelsberg,* 
(analyses 1, 2, 8, and 4,) and Siegert,+ (analysis 5,) for Stilp- 
homelane: 
: Si lo 6fe «=6rFe «6OMg «6Ga KNa Tf 
* 4819 816 1... 8705 884 119 1... 695 run 
f % 4650 719 .,.. 3389 189 020 .... 7-90 poe Dake nae ‘ 
: 3. 4543 588 4... 3538 168 O18 .... 92 bites Silica 
4 4617 588 2... 3592 267 .... O75 879 From. Weilbure' i 
: ; ; : rom We g m 
6 4207 492 4198 1... 094 167 ..., sai} Wash 
Siegert assumes the iron to exist as sesquioxyd while Ram; , 
melsberg gives it as protoxyd, with the remark that if it be cal- 
culated as Fee, the analyses will give an excess, and therefore 
. Perhaps it only exists as protoxyd in the mineral. 
It is evident from the results of analyses 1 to 4 that the stilp- 
nomelane analyzed was not entirely free from foreign substances, 
and Rammelsberg mentions that it may possibly have been mixed 
with some chlorite, and that this is the reason for the difference 
in the results, 
Analyses 8 and 4 correspond very closely with the analysis of 
c s . . . . ° 
acids, while chaleodite is entirely decomposed, may be to the 
eme delicacy of the scales in the latter; the same cause wil 
account for the difference in hardness. The specific gravity is 
0-3-4 Glocker, or according to a more recent determination 
by Breithaupt, 2°769. Chaleodite has a density of 2°76. Stilp- 
, the marked similarity in chemical, as well as in many of the 
priysical characters of these two minerals renders it not improba- 
that a reéxamination of pure stilpnomelane would pera’ 
those discrepancies which at present prevent their being unt 
Under one species, 
Yale Analytical Laboratory, Dee. 15, 1857. 
] 
The fact that stilpnomelane is but imperfectly 4 part. by 
ue : 
i 
E. 
& 
S 
a 
1a) 
4 
% 
a 
< 
é 
Es 
&, 
e] 
e 
Qa 
3 
a>) 
5’ 
4 
é 
3 
* Poggend. Ann,, xliii, 127. _ 
Rammelsberg, Mineralogie, Fifth Suppl. 208. 
SECOND SERIES, VOL, XXV, NO. 74,-——-MARCH, 1858, 
26 
