On Fri, 02 Jul 2004 07:53:30 GMT, Seppo Renfors wrote:
Gary Coffman wrote:
On Thu, 01 Jul 2004 12:10:10 GMT, Seppo Renfors wrote:
Gary Coffman wrote:
On Tue, 29 Jun 2004 07:05:25 GMT, Seppo Renfors wrote:
This has a good story about the Great lakes Copper deposits.
http://www.geo.msu.edu/geo333/copper.html
As that article notes, 14 billion pounds of copper have been removed
from the area since the ancients were working copper there. Let the
enormity of that number sink in. There was an *awful lot* of copper
there in ancient times, much of it easily accessible from the surface.
My main interest was to show the formation of the copper deposits -
the volcanic activity that melted it (and other minerals with it).
Silver is/was found in fair quantities alongside the copper. What
isn't known - because nobody cares to find out, is the composition of
the metal used in the artefacts. It is ASSUMED to be pure copper.
The presence of silver inclusions *proves* the native copper was not
melted after being deposited.
...but only for that piece - not for any other piece. Further more
IIRC there is a method of laminating copper and silver sheet and
carving through one into the other. It is a Japanese technique IIRC.
It requires being heated under pressure, to the point the silver just
starts "sweating" and it brazes the sheets together. So silver in
copper can also be deliberate - as decoration.
It is called silver brazing (or more commonly, but incorrectly, called
silver soldering). It is a common technique used to join pieces of
copper. Pressure is not required. A temperature in excess of 800F
is required for brazing to occur (by ASTM definition).
Native copper is deposited by chemical
means, not volcanic melting and extrusion.
I already posted this earlier. It disagrees with you:
http://www.geo.msu.edu/geo333/copper.html
"chemical" doesn't get a single mention.
Actually, it doesn't disagree with me. It says the copper
was carried in an aqueus solution from great depths
and deposited in the vents, fissures, and voids of the
iron bearing rocks above. The pertinent chemical
reaction involved is
CuSO4 + Fe(Metal) = FeSO4 + Cu (Metal)
If you were knowledgeable of the chemistry of copper, this
would have been obvious to you. If you had read any of the
many geochemical references in the links already provided
in this thread, it would have been spelled out for you in
excruciating detail.
This naturally chemically
refined material is extremely pure copper. Here's a quote from the
Caladonia Native Copper Mine literature;
" The term "native" as used by mining men is synonymous with "pure",
"unadulterated" or "virgin". Keweenaw copper was found in a state of
such purity that a piece brought from underground could immediately
be beaten into pots and pans without smelting or refining."
This does not make a claim of "chemical" anything. Copper Sulfate
(Bluestone; blue, Roman or Salzburg vitriol) is soluble in water - but
dries to a blue crystal or powder. There are just nowhere near the
amount of acids or ammonia to it to be dissolved in!
Again, I suggest you consult a good text on geochemistry. If you
feel such a text would be too daunting, then just look for descriptions
of the production of Ziment Copper, or how the leaching ponds at
Parys mountain operated. These processes mimic the natural
geochemical processes at work at Keweenaw.
Gary