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Cleaning native copper

Posted by Kyle Eastman  
avatar Re: Cleaning native copper
January 16, 2012 07:06PM
Finally, two sets from pieces I gave a bath in Tarn-X. With this method, they edges were kept distinct, and the whole process took much longer. However, shortly after being removed and rinsed, they took on a crazy iridescent sheen. I tried a second time, and ended up with less of the iridescence, but it is still there. The thing is, this sheen doesn't show up right away, but rather a few hours after. I think if I do something to dry them off and perhaps coat them, it won't be so prevalent. Still, they end up with a bright patina that I am not really fond of.

Again, I don't have in front of me the location. These are both smaller pieces, like the Phoenix piece.

open | download - Copper Specimens_024.JPG (119 KB)
open | download - Copper Specimens_025.JPG (140.8 KB)
open | download - Copper Specimens_026.JPG (170.5 KB)
avatar Re: Cleaning native copper
January 16, 2012 07:07PM
The last piece, another Tarn-X job.

open | download - Copper Specimens_027.JPG (86.6 KB)
open | download - Copper Specimens_028.JPG (108.5 KB)
open | download - Copper Specimens_029.JPG (83.2 KB)
Re: Cleaning native copper
January 16, 2012 11:21PM
I don't think that this cleaning method has been mentioned.

When we came across Keeweenaw coppers that were enclosed in basalt, we would heat them up in the oven at highest heat, and them drop them into a bucket of cold water. Many treatments were necessary, but with luck, most of the basalt would fall away. No acid, No neutralization needed.

It was thus possible to convert a worthless specimen into a five dollar specimen via ten dollars of effort.

avatar Re: Cleaning native copper
January 16, 2012 11:56PM

I like your idea a lot. Sometimes we'd find that just using a hammer to shatter the basalt was the only effective means, but the thermal method seems a lot more elegant - plus you get to heat things up way beyond safe limits & throw them in water! R-R-R! More power!
avatar Re: Cleaning native copper
January 17, 2012 02:52AM
Bart Cannon Wrote:
> I don't think that this cleaning method has been
> mentioned.

Actually, it has been mentioned in many books and research papers over the years. This was the method used over 5,000 years ago by the ancient miners of the Copper Country who wanted to separate copper from basalt. It is said that they would build a large bondfire along a stream or lake and toss copper into it to heat it up. Once hot, they would throw ice cold water on them and supposedly, the contraction of the copper would shatter the rock, sometimes with explosives results. I am told that it does work, although it's not the most effective way to remove basalt from copper.
Re: Cleaning native copper
January 17, 2012 06:54AM

I'm on the edge of my chair. What IS the best method to remove basalt from Michigan coppers ?

One method I've thought about is known as the "electromagnetic pulse pulverizer". I worked with a guy who was developing it to liberate diamonds from kimberlite. He was able to liberate orthojoaquinite crystals in fine grained syenite for me from a rare earth deposit in Alaska.

He went on to different dreams, and told me how to build the device. It required high voltage capacitors the size of oil drums and a the switch was driven by a bullet. More hazardous than the bucket steam bomb I once employed on coppers.

I have done much research on ancient indian mining in the Keeweenaw. I even worked with Dr. Rapp on the trace element chemistry via WDS on Michigan coppers with the hope that we could establish trade routes and copper sources for copper artifacts in North America. I had crazier hopes. I wanted to verify Pre-Columbian trade contact between Europe and the Keeweenaw people.

We determined that trace chemistry was hopeless via WDS, and even hopeless via mass spectroscopy because the chemistry of Michigan coppers changes by the foot in the mine. My final conclusion was to use silicate inclusions as fingerprints, but no European museum would allow messing with their artifacts.

Much the same with another of my projects. Determining the provenance of the spear point in Kennewick Man's ilium. Curators mostly just want to keep stuff pristine in their museum drawers. When I was examining K-Man's ilium in the Burke Museum with my Optivisor, hands behind my back, I got tapped on the shoulder and told "you are too close".
Re: Cleaning native copper
January 17, 2012 12:55PM
Bart: What was the temperature setting on your oven, and how long did you leave them in there before putting them in the water? You're talking about copper with just certain kinds of rock? Since I have no idea what you were talking about with those 50 cent words in your last post and I don't know what the difference is between a green, brown, black rock/matrix??? Can it be dangerous to put some rocks in the oven? Not a rocket scientist...........SCOTT:.....How long did you leave the copper in the Tarn-x? Did you rinse them in plain water or water with baking soda? Vinegar and Salt? ......Thanks guys....Bill
avatar Re: Cleaning native copper
January 18, 2012 01:46AM
Bart Cannon Wrote:
> Paul,
> I'm on the edge of my chair. What IS the best
> method to remove basalt from Michigan coppers ?

Unfortunitely, one of the best ways to remove basalt is also one of the most dangerous; that's to use HF, which I do not recommend anyone using!! As I mentioned before, one of the spring loaded centre punches works well, as does just carefully chipping away at the basalt. I know that can be time consuming, but at least you'll live to see tomorrow.

Bill, I believe what Bart is talking about are the different coloured basalt matrix one can find attached to the coppers of the Keweenaw. They are actually quite easy to distinguish; green is epidotised basalt. Black is the common colour for basalt. A chocolate brown/reddish coloured basalt is where the majority of the "good" minerals were found during the mining days. The Pewabic Lode in Quincy and other mines nearby was this reddish/brown colour and it was a sign to the miners that they were in potentially good ground.
Re: Cleaning native copper
January 18, 2012 03:40AM
Mr. Paul: Once again I must thank you for making things a little bit easier for me to understand. I do apprreciate that. Bill
Re: Cleaning native copper
January 18, 2012 05:23AM
Bart has not answered, and I've never tried it, but I'll keep it for future reference, certainly. My, and I guess most ,ovens hit 550 degrees. That wont melt copper or basalt, so crank it...How long, don't know, but I bake bread for 50 minutes, and I would suspect a rock if small, would be pretty hot in 50 minutes, or less, of course, depends on the rock... And certainly, drop in water ASAP, I'd guess, or you lose heat. Winter would be a good time to do that, heat your house. Summer's hot enuf w/o that...

Re: Cleaning native copper
January 18, 2012 06:04AM
Your Phoenix specimen looks like most of the pitting and rough surface may be do more to 150+ years of oxidation on the pile then the acid. To long in the hcl will give the specimen a melted look. If the piece wasn't totally enclosed by calcite it's probably oxidation. A lot of Keweenaw copper has a thin layer of calcite around it and etching away the calcite will leave that small gap that can be exploited in removing the matrix. Unfortunately with some specimens it's almost as if the matrix is part of the top layer of copper. Specimens from the Seneca #1 have been the most frustrating to clean for me. You might reduce or eliminate the iridescence on the acid cleaned copper by quickly drying it once out of the final rinse. My results have been mixed. Some copper appears more susceptible, but a quick blow off and follow up with a heat gun, from prior incidents don't let your wife catch you with her hair dryer, or placed in direct sunlight on a warn day seen to help. Tarn-X is made by Jelmar in Skokie Illinois. The MSDS shows it it contains Sulfamic Acid and Thiourea, but the mixture is listed as proprietary. If your interested in obtaining Sulfamic Acid or some other tips PM me. Spent 30 years collecting in the Keweenaw.
Re: Cleaning native copper
January 18, 2012 07:15AM

My copper baking was done in 1963 and 1964. I was 13 years old. The oven was also about the same age. I don't remember paying any attention to the operating conditions, but I suspect 300 degrees would be enough to get the rock hot enough for thermal shock and plenty of differential expansion of dissimilar materials.

At 50 cents per 50 cent word, I think you now owe me $2.00.

As for HF, I would be dis-inclined mostly because of the expense of the HF versus the value of the copper specimen.

In previous decades I frequently used HF and only suffered one wound. Somehow a drop found its way to my cuticle and a day later that area felt like a bruise. One tip about HF is that you should never use rubber gloves. They give you a false sense of protection, and they always have a pinhole leak. Tongs are the only way, but you still run the danger of a splash

If you use HF you should always have a tube of calcium gluconate antidote gel very handy.

My use of HF declined precipitously after I bought a CRC tome on lab safety which had dozens of color photos of HF wounds. The ones showing melted eyeballs are quite life changing.

avatar Re: Cleaning native copper
January 18, 2012 11:59AM
Jim Gawura Wrote:
> Specimens from the Seneca #1 have been
> the most frustrating to clean for me.

That's not surprising, considering the copper in that area of the Keweenaw around Seneca/Mohawk has a higher concentration of arsenic than most places. No matter what one does in attempting to clean a specimen from there, it never really comes out great.
Re: Cleaning native copper
January 18, 2012 11:56PM
I made a mistake.

Seems that it's Bill Boehm who owes me $2.00 for my 50 cent words, not Mike.

Hard to keep track, isn't it. I don't believe that it was me who mentioned "green, black, brown rocks" enclosing coppers.

I do have another suggestion about cleaning coppers that would require $25 dollars of effort to produce a $5 copper.

My EWL air abrasive station has, in addition to its bead blast guns, a very powerful micro jack hammer. It will remove chunks of rock when set to high pressure, and can work more delicately at lower pressure.

Still not an economic solution for coppers, but there is something therapuetic about punishing matrix.

Re: Cleaning native copper
January 19, 2012 02:18AM
Bart, you're wrong. I didn't recognize about 15 or 20 words @ $.50 I do have a question that is very important to me if any of you will respond to it. Is there any particular rock? matrix? that I should not put in a oven and heat it up? Crystals? What about the specimens that you say may have arsenic in them? When working with specimens that have arsenic in them do I have to worry about dipping them in Muratic acid or Tarn-x, vinegar and salt? Do I need to wear a mask or gloves when working with it? Can I tell by color or texture if it has arsenic in it. I am strictly a 73 year old beginner that knows nothing about chemicals or minerals so forgive me if I ask dumb questions. I am going to start a site on talk pages about copper artifacts in the Keeweenaw. Bill
Re: Cleaning native copper
January 19, 2012 02:49AM
Paul: I went to the talk pages, scrolled through all nine of them and there were no topics about the Keeweenaw to jump into. I could not find out how to start a new post.

Paul: I scrolled through the nine talk pages and there wern't any topics about the Keeweenaw that I could add to. I could not find a way to start a new post. Can someone tell me how to start one? Thank you.
Re: Cleaning native copper
January 19, 2012 03:47AM
I'm new enough at this too, but I'd venture to say you can put any rock in an oven. Lava runs in the vicinity of 2000 degrees F, give or take, right? So don't worry, you've got lots of leeway there. Some cherts, I hear, have moisture in them and don't make good campfire rocks because they can blow up, but i have never known of that happening. If others could weigh in on that i'd like to hear...You are talking at most fist sized pieces in an oven, aren't you, I'd guess. Baking a turkey sized hunk of pure arsenic may not be wise, but the little in copper, I can't see any danger, IMHO.
I also don't think there are too many minerals that would ever need, or could withstand, this kind of abuse. horrible cruelty!
There was a great thread on safety just recently. Go to the home page, upper right,and at 'search for' scroll to messageboard and type 'arsenic and cinnabar' and that thread will come up. It'll put your mind at ease. Mineralogy is not extreme sports.not usually.
Muriatic acid is dicier stuff. I only use it outdoors.

Bart, great comment on 'punishing matrix', so true!

Re: Cleaning native copper
January 19, 2012 04:33AM
Went to localities, to top right, typed in copper artifacts and the keeweenaw, hit search, clicked on new topic.......came back at me "sorry, you do not have permission to post/reply on this forum" ! getting really frustrated.
Re: Cleaning native copper
January 19, 2012 05:35AM
Localities might work better if you give it less. i found that using one key word would get me close, then i could scroll though what came up, i.e. type in just a county, then when all the states came up, scroll to michigan and you might find what you want. Managers could help more, but this has got me through .
Re: Cleaning native copper
January 19, 2012 03:28PM

I would avoid oven treatments of mercury ores, thallium ores and realgar bearing rocks. I don't think that arsenopyrite will release arsenic oxide fumes at 300 degrees F.

There are extensive discussions about the dangers of minerals someplace on the website.

Good news. I've decided not to bill you for my 50 cent words. Just reading them is enough penance.


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