Floating
Copper
I used to work on the docks at the US Corp of Engineers station on
Minnesota Point and recall walking past this monument that was
sitting in some obscure corner of the station. I was fascinated by
the immense size of it and always wondered why it was out of public
view. Well now it has a new home.
What you see before you is a rare example of a piece of float
copper dredged from the Keweenaw Waterway in Michigan in 1937 by
the dredge New Jersey. The dredge was under contract with the US
Army Corp of Engineers office in Duluth.
Can copper float?
No, not in the traditional sense of the term. Float is a geological
term used to describe any material that has been carried by erosion
away from its 
spot of formation, as in this
example by glaciation. This process is very important to
prospectors who track “float” patterns to its source.
Native copper is very abundant in the Upper Peninsula of
Michigan in basaltic lava and interlayered sediments formed
approximately a billion years ago. Freed from the rock by
weathering, this copper can survive long transport by glaciers and
rivers because of its tenacity and relatively low chemical
reactivity. Float copper is found all states that have received
glacial drift from the Lake Superior region.
In 1895, a Wisconsin geologist, Roland Salisbury, made a
detailed study of float copper in Wisconsin. He states "specimens
of 40 to 50 lbs, weight are not uncommon".
Here are a few of the more notable drift copper finds from
Wisconsin, as reported by Salisbury and others.
- ASHLAND COUNTY: Salisbury (1885) reports the find of a 100 lb
copper boulder from Outer Island.
- BAYFIELD COUNTY: The largest nugget of float copper reported
from the Wisconsin is a boulder weighing 1,700 lbs. found in the
bed of the Sioux River about 6 miles south of Lake Superior
(Salisbury, 1885).
- DANE COUNTY: A 30 lb. nugget of drift copper was found in a 20
foot deep well in Madison (Salisbury, 1885).
- DODGE COUNTY: A nugget of float copper weighing 487 lbs. was
found near Hustiford (Irving, 1882).
- ROCK COUNTY: A 114 lb. nugget of drift copper was found at
Newark (Salisbury, 1885).
- SHAWANO COUNTY: A 970 lb. mass of drift copper was found in a
gravel pit 2 miles south of Pella (Wisconsin Geological Survey
files).
TO LOG THIS CACHE:
1) What month was this float copper discovered?
2) Based on the weight given and current commodity price of copper
calculate the current market value of the piece of float
copper.
E-mail me the answers
HERE.
Sources: 
- Irving, R.D. 1882, "Minerals of Wisconsin" Chapter II in
Chamberlain, T.C. Geology of Wisconsin Survery of 1873-1879, Vol.
I, p. 309-339.
- Salisbury, Rollin D., 1885, "Notes on the dispersion of drift
copper", Wis. Acad. Sci. Arts and Letters, Vol. 6, p. 42-50.
- Wikipedia: Copper
- Leaverite News Articles by William S. Cordua UWRF - Floating
Copper 1997
Links: