CHAPTER II.
MINERALS OF WISCONSIN.
BY R. D. IRVING;
In this chapter are listed all the mineral species that have come to
my knowledge as existing within the State of Wisconsin.    A brief
list of Wisconsin minerals by the late Dr. Lapham is published in the
second volume of this series.' The latter list was intended, however,
merely as preliminary, and includes rather the results of Dr. Lap-
ham's own previous researches, than those of the investigations of
the Geological Survey. It is thus naturally verqy defective, omitting
the names of a number of the most abundant and important of Wis-
consin minerals, besides including, the names of several species Whlose
existence has not been substantiated by the investigations of the Geo-
logical Survey. It is not, of course, pretended that the present list is
a
complete one; it is merely a record of observations to date.2
Immediately after the name of each mineral, I have added its
chemical formula. For the physical properties reference may be
made to any good manual of mineralogy. The principal optical and
microscopic characters of the rock-forming species as seen in the thin
sections, so far as is necessary to an understanding of the rock de-
scriptions of this series of reports, are, however, included.'
The order in which these species are successively referred to is that
of Dana's Mineralog~y, and is indicated in the following preliminary
enumeration:
Native Elements.                 Sulphides.
1. Gold.                         7. Galenite.
2. Silver.                       8. Bornite.
3. Copper.                       9. Sphalerite.
4. Iron.                         10. Chalcocite.
5. Sulphur.                     11. Niccolite.
6. Graphite.                     12. Pyrite.
I Vol. II, pp. 207-30. Annual Report for 1873.
2May, 1882.
3 For the optical and microscopic characters of the several rock-forming
species,
[have used the works of F. Zirkel, H. Rosenbusch, G. W. Hawes, and R. Pum-
pelly, as well as my own experience.