We £7. Hobbs—Mineralogical Notes. 123 
With the exception of the face y, which is small, the reflec- 
tions are good. Figure 1 illustrates the habit of an individual 
on which all the forms observed are represented. However, 
most of the crystals are stellate twins composed of three or 
more individuals. Figure 2 shows a cross section of such a 
twin composed of three individuals cut parallel to the basal 
pinacoid. 
As the galena layer is nowhere found on the gangue material 
but occurs only on the surface of the cerussite crystals, it is. 
clear that its formation is due to alteration of the cerussite by 
removal of carbon dioxide and addition of sulphur, probably 
through the action of sulphuretted hydrogen. It is therefore 
an Umhiillungspseudomorphose after cerussite. The pseudo- 
morphs of calcite after cerussite from Grube Kautenbach bei 
Bernkastel show in cross sections a paper-thin layer of galena, 
which according to Blum* was formed on the surface of 
cerussite crystals. Calcite has been deposited over this and, 
after the removal of the cerussite, under it also. The Bernkas- 
tel pseudomorphs would thus seem to have been, in their first 
stage of alteration from cerussite, identical with those which 
are here described from near Missoula. 
2. Barite and Manganite from the Lucy Mine, Negaunee, Mich. 
In the spring of 1894, Mr. J. R. Thompson of Ishpeming, 
presented to the Museum of the University of Wisconsin some 
large specimens of barite and manganite. They were taken 
from the Lucy mine, formerly the McComber mine, at Negau- 
nee, Michigan. This mine is located in the S. W. cor. of Sec. 
* Blum, Pseudomorphosen, iii, p. 212. Cf. also Roth, Allgemeine u. Chem- 
ische Geologie, i, p. 188. 
