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Cleaning native copper

Posted by Kyle Eastman  
David Von Bargen January 19, 2012 04:45PM
You start locality talk pages from the locality page (Discussion button).
Anonymous User January 19, 2012 04:46PM
Thanks Bart for the info on those ores and for releasing me from my debt. I guess I can say I'm indebted to you. :-D
Anonymous User January 22, 2012 03:45PM
Can someone help me please. It seems that this is the only place I have been able to get a response from anyone. I (thought) I registered as I was supposed to, to navigate the website, then thought maybe I didn't so went back and it said user name already in use. I (thought) I filled out the box on home page profile that said I would get permission in 48 hours to be able to use talk pages. I (thought) I sent an email to Jocyln Ralph about my troubles and frustrations and wanting help, but I hear from noone except here on this forum. I appoligize for using this site other than for cleaning questions. I'm excited about learning more about collecting and all it's virtues but am exaspertated. Bill:-S:-((td)
David Von Bargen January 22, 2012 05:18PM
If you are logged in, you should be able to start a new talk page from a locality or mineral page (from the Discuss button below the navigation bar at the top of the page). Topics that are not related to a particular locality or mineral should be started in other fora and not on the talk pages.

You cannot start a new topic for the talk pages from the fora, they need to be started from mineral or locality pages.
Paul Brandes January 22, 2012 08:45PM

I'm sorry you are having issues with the site, but please don't be discouraged. Remember, everybody at one time was in the same situation you are in now and by trial and error, you will learn how to use the site. I've been coming here for many years and I still learn new things about the site.

Now to answer your question about the talk pages: I attached a photo below to show what you should see to create a talk page for the Keweenaw Peninsula. You should be able to see the toolbar under the locality name. Highlight the "Discussion" tab to make the "Create Talk Page" drop down appear. Just click on that and you should be able to create a talk page for the Keweenaw or any other locality or mineral.

open | download - MindatTalkPage.png (341.3 KB)
Scott Sadlocha January 22, 2012 10:24PM
Try not to get too discouraged. Once you navigate the site a bit, you will get the hang of it a bit more. There is a lot of functionality here and it takes some getting used to. Also, one other thing I should mention--most of the time, folks here are fairly good at responding. However, this time of the year, you might not get a response as quickly as you normally would. Right now a lot of folks are getting prepared for, or are already in, Tucson, Arizona, for the largest mineral show in the world, which happens yearly at the end of January and beginning of February.
Scott Sadlocha October 07, 2012 07:51PM
Revisiting this page after quite some time to get a few tips and answer a few specific questions. I spent some time in the UP a couple weeks back, and now I have some specimens I want to clean.

1. With a vinegar cleaning method, is the vinegar used full strength or diluted? I have heard it takes longer to soak and clean. How long should it take?

2. Will a sulfamic soak remove calcite or just do more of a cleaning?

3. Will any of these acid bath types of cleaning (HCl, sulfamic, vinegar) damage pumpellyite?

The reason for my questions are the specimens I brought home. I have quite a few pieces with infilled veins where there is much prehnite present, and I suspect a decent amount of copper. I need to remove the calcite infilling, but I don't want to damage the copper. If it comes out shiny, that is fine, I just don't want that "burnt" look that I have experienced with HCl. I have a few pieces of this type of prehnite/copper that others have cleaned, and it is apparent the calcite was dissolved, but they look very nice. I am confident that I have at least a few pieces like this and want to get them opened up.

I also have one miniature sized piece with a very small pocket on one end of it. Looking at the edge of the pocket, it looks very much like radiating pumpellyite. However, beyond this the entire pocket is infilled with calcite. I want to remove it and not damage anything else.

I also have some pieces with native copper, and I need to spend some time trying to figure out how to clear it out, but I am focusing on the two types of pieces I mentioned above first.

Scott Sadlocha October 09, 2012 07:04PM
Anyone have a chance to check this out yet and read my last posting? Any information would be greatly appreciated.
Dan Fountain October 10, 2012 12:43PM

I'll try to answer from my limited experience.

1. Generic white vinegar in the US is usually 5-8% acetic acid (sez Wikipedia). That's pretty dilute already; I don't see any reason to dilute it more.

2. Sulfamic acid will definitely remove calcite. I've used concentrated and dilute - usually using concentrated (saturated solution) when I'm not expecting to find copper under the calcite and diluting a saturated solution about 4:1 if I'm removing calcite from copper. Whatever you use, check it often - starting at every few minutes, to every few hours, to several times a day until you get a feel for how fast it's working on your particular material. I think that rinsing has been stressed in this thread before...

3. Dunno.

I've left some copper crystals that I have found free of matrix in their native state with patina - I just remove dirt and surface grime with detergent and a soft brush. The "scrubbing bubbles" produced by a metal catalyst such as copper in hydrogen peroxide do a good job of cleaning without changing the surface. This also works for cleaning red hematite mud from those delicate needles of pyrolusite, but it may darken some of the bright silvery crystals slightly.

Hope this helps. Whatever you try, don't do your best specimen first.

Scott Sadlocha October 10, 2012 05:46PM
Thanks for the update Dan. I am going to give things a try this weekend to see what I get. With some of the copper I found, I am going to leave it alone, because a soak will end up leaving me with a bunch of small bits of copper, I believe. But there are a few pieces I really want to check. The prehnite pockets are one, but I also have a couple pieces from the Phoenix Mine where there is visible larger copper sticking out of a decent amount of calcite, which gets me wondering what might be in there. I have a handful of pieces that I am optimistic about. I also have some junker pieces I can use for testing.

Since the pumpellyite is a silicate, I am not expecting any issues with a soak, but I want to make absolutely sure before doing so. I am really interested to see how this would turn out, and I only have one specimen like this.

I know what you mean about cleaning with a brush. This is my first step, and I usually evaluate after this to see if this might be all that is needed. With those pyrolusite specimens we collected, I think that is all that will do. Some of those are absolutely stunning after a good cleaning. I think the rhodo we collected (altered or coated) is going to get a blast from a cleaning gun to clean out the crevices. I will let you know how it goes.
Paul Brandes October 10, 2012 06:28PM
I saw your question on Oct. 7 but haven't had the opportunity to respond; that little thing called work always seems to get in the way of fun activities!!!! :-(

Anyway to your questions:
1) Pretty much what Dan stated. Normal white vinegar you can buy at any grocery store will work, but it is slow and as long as you can handle the acetic acid odour you'll be fine.

2) Sulfamic will dissolve any carbonate, including calcite; however, I have found that cold sulfamic acid will not dissolve the calcite as aggressively as warm or even room temperature acid, and not nearly as fast as HCL. As Dan stated, the key to using sulfamic or any acid is to babysit the pieces and check them every few minutes (or seconds in some cases) to make sure you don’t remove more than intended. A quick dip and rinse will clean calcite, anything longer and it’s bye-bye carbonate!

3) Pumpellyite is not affected by HCL, so you'll be safe with either HCL or sulfamic. Sulfuric will dissolve pumpellyite slowly, and HF will dissolve it almost instantly. As far as prehnite; be careful placing a specimen in HCL. It will attack the specimen slowly which will whiten any crystals and eventually turn them into powder if you leave them in too long, unless your aim is to remove the prehnite. A quick dip in HCL doesn’t seem to bother them so long as it’s rinsed properly afterwards.

Have fun and post a few pics of the results for us…..
rufus December 18, 2012 03:27PM
How do you keep it clean is the biggy ?????
have a look at the samples In have - I want to keep them this bright as this is how they came out of the ground !!
open | download - DSC_0419.jpg (885.5 KB)
Rock Currier December 19, 2012 08:52AM
The only way to keep it bright is to keep oxygen and other active gasses like SO2 NO2 away from the copper. That means coating it with something that will do that or putting it in a container with an inert atmosphere. It doesn't look much like copper in the image, at least not on my monitor.

Rock Currier
Crystals not pistols.
Reiner Mielke December 25, 2012 05:40PM
One thing I have found that usually works where most acids fail is a stuff called Wright's Copper Cream, it is made in Gurnee, Illinois. However you cannot use it on delicate specimens since you have to apply it with a brush ( I use a toothbrush). Also it is slow and not suitable for mass production but you can be selective about what area on the sample you want clean. Another unusual thing about this stuff is that the copper cleaned stays clean longer than with other methods, but like all methods eventually the copper will tarnish. This method does not however work on high arsenic copper I don't know of anything that will clean that stuff.
kishor September 21, 2013 11:20PM
dear sir
i have pure copper sample and i have to do EBSD. but after polishing sample gate corroded and tarnished. so can you tell me method to preserve copper sample after final polishing with collidel silica without affecting crystal structure and plane. so i can do the texture study. thanks
Reiner Mielke September 22, 2013 01:11AM
Hello kishor,

You could try a light coating of silicon oil or silicon lubricant? Not sure how that will affect EDSD though. Another possibility is to storing the sample in an inert gas such as argon or helium.
Jake Harper July 20, 2014 08:05PM
Hi guys,
Recently picked up a small collection with some Michigan goodies including these three coppers.
Each one is well xled but they have various coatings that are not the most attractive. I realize strong acids are not an option, however I am wondering if something mild like a diluted citric acid might produce results without a burn? Any help will be greatly appreciated.


All knowledge is vain, except where there be work
All work is empty except where there be love
open | download - cu1a.JPG (155.2 KB)
open | download - cu3a.JPG (167.2 KB)
open | download - sponge_copper2.JPG (177.7 KB)
Rob Woodside July 20, 2014 08:10PM
Nice Coppers!!! I'd leave them alone.
Alex Homenuke July 20, 2014 09:11PM
The second one has an outstanding patina and would be seriously devalued if you cleaned it.
The first one also looks pretty good as is.
The third one could be improved (IMHO) with careful iterative cleaning. You might try a series of quick dips in phosphoric acid, followed by copious rinsing with water. Another way is using an artists soft brush with the acid to take of enough of the oxidation to show the coppery color, but let it retain some of the patina. There are diverse opinions about cleaning copper.
Paul Brandes July 20, 2014 09:23PM
Personally, I'm with Rob; leave them alone! Too many folks are quick to clean native copper to get that shiny penny look, but not only does it then make copper look unnatural, it also seriously degrades the value and "classic" appearance of native copper that so many collectors desire.

I'm not sure about the first photo, but 2 and 3 appear to be Laker Coppers which, with any type of non-gentle cleaning methods, will fall apart.
Alfredo Petrov July 20, 2014 09:52PM
Coca cola, with its combination of dilute citric and phosphoric acids, is another good copper cleaner, if you run out of vinegar.

It also attacks apatite. Guess which mineral teeth are made of? Something to think about while watching the coke do a good job on your coppers :-D

To slow down the tarnishing of copper after cleaning, some collectors and commercial mineral cleaners dip it in a solution of an oxidizing salt, like potassium dichromate, for example, to create a thin protective skin of cuprite over the surface of the copper. The red cuprite film deepens the apparent color of the copper too. The results can be quite lovely but, although Nature herself sometimes coats copper with cuprite, doing it on purpose produces a no-longer-completely-natural mineral specimen. And chromium salts are rather toxic too. I do not recommend this procedure, but be aware that it may have already been done to some native coppers on the market.

Edited 1 time(s). Last edit at 07/20/2014 10:02PM by Alfredo Petrov.
Jim Gawura July 21, 2014 02:31AM
Although not shiny copper I would not touch them. All three have beautiful crystal structure and are not encased in matrix. Just like a lot of copper collectors love. Au naturel.
Jake Harper July 21, 2014 05:02AM
Thanks very much for the advice Rob and everyone.
I will certainly go with the consensus and leave these coppers just as they are.

And yet once again the charges of save a few more specimens from the impending doom of the uneducated.


All knowledge is vain, except where there be work
All work is empty except where there be love
Larry Hulstrom June 10, 2016 11:47PM
Greetings all - Following my retirement last year I am now getting back to doing more enjoyable things. A few years back I acquired a 22# piece of copper from behind a workbench at the home of a fellow rockhound to whom I was helping to settle his estate. I recognized the piece (see attached pictures) as likely one from the UP of MI. Being a native of the UP but having spent most of my career out in WA State I am still an active rockhound and participant in our local club. I would like your advice on how to approach cleaning this specimen to remove as much of the matrix (basalt/quartz/calcite, etc) as possible without damaging it. Having seen some specimens such as this in museums I have high hopes that this may be of similar quality. It appears to have copper embedded in the quartz vein matrix so I have been leery about doing to much to it. I would appreciate any feedback you can provide. I have read the preceding discussions and hope that some of you still are around to respond.

Paul Brandes June 11, 2016 02:00AM
Welcome to Mindat, Larry!

Your specimen does resemble those that come from the Keweenaw Peninsula of Michigan. One of the first things I would do is check for any copper crystalisation as that will determine what cleaning solutions to use. From your photos, I'm not seeing any crystals so what you have appears to be a normal lump of native copper with attached matrix. With that mixture of matrix (calcite/quartz/basalt), there are few options you can use to clean it. If you read the previous posts by myself and others, that should point you in the right direction.
Jim Gawura June 11, 2016 04:52AM
Probably the best way to try cleaning it would be to scrub it and hose it off good. Then submerge it in vinegar, or part of it and see if it fizzes. The vinegar will attack any calcite. It also won't screw up any possible crystals lurking underneath. A real possibility is that you will only brighten the exposed copper. A lot of the ore has basalt directly on it, also quartz, and prehnite are fairly common associations. The acid will not affect any of those. At times a thin layer of calcite will be directly in contact with the copper and if this is etched out you can sometimes break off any other outer coating. Let it soak for at least a week. Check it carefully every now and then and observe it closely for any differences. Vinegar works extremely slow.
Good luck,
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