Mineralogical Contributions — Hobbs. 185 
"Alunogeri" from Cripple Creek District, Colorado. 
Analyzed by W. O. Hotchkiss and R. M. Chapman. 
Hotchkiss. Chapman. 
AFO 3 8.28 9.41 
MgO 14.44 4.40 
SO 3 34.06 43.74 
H 2 43.86 43.86 
100.64 101.41 
The close similarity of the two minerals makes it diffi- 
cult to obtain a perfect separation of them, and this chiefly 
explains the variation observed between the analysis quoted. 
J. Crystallized Copper from Soudan, Minn. A very 
interesting and almost unique example of metallic copper in 
association with hematite is the occurrence at the Minnesota 
mine in the Vermilion iron-bearing district of Minnesota. 
As this occurrence does not appear to have been figured, 
the beauty of the films and trees seems to warrant its repre- 
sentation, which is given in plate xi. Although the occur- 
rence has been described,* it does not appear to be well 
known, the place of publication not being well known to 
mineralogists. The occurrence is also casually mentioned 
by Clements. t Together with the hematite in association 
with the copper are found cuprite, malachite, and azurite. 
The copper minerals occur, in a narrow seam in brecciated 
hematite, the only place where it is found in the region or 
in any of the iron-bearing districts of lake Superior. This 
rare occurrence should be considered in connection with the 
discovery by Haworth of thin films of native copper in red 
clay shales near Enid, Oklahoma. $ In both occurrences the 
copper is extremely limited and generally found in thin 
films upon apparent fissures. Though the Soudan occur- 
rence was apparently not known to Haworth at the time 
his paper was read, he. has suggested the same explanation, 
namely ; the reduction of the copper by the oxidation of the 
ferrous iron compound. 
*J. H. Eby, and Charles P. Berkky. Copper minerals in hematite 
ore. The Year Book of the Society of Engineers, university of Minne- 
sota, 1897, pp. 108-117. Reprinted from the Proceedings of the Lake Su- 
perior Mining Institute, vol. 4, 18%, pp. 69-79. 
t J. Morgan Clements. The Vermilion Iron bearing district of Minne- 
sota. Mon. 45, U. S. G. S. 1903. po. 112, 134. N. H. Winthell Metallic 
Copper. Final report, Minnesota Geological Survey, vol. 5, p. 885, 1900. 
