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Flambeau Mine chalcocite

Posted by Raymond Lasmanis  
Flambeau Mine chalcocite
November 14, 2011 05:56PM
I have had a beautiful violet-purple patina chalcocite in my collection. Recent examination shows the chalcocite coated by a brownish very fine powdery coating. Of course the patina is gone. Has anyone else experienced this?
avatar Re: Flambeau Mine chalcocite
November 14, 2011 06:02PM
    
This is the cabinet growth on Chalcocites. The scuzz is too poorly xled for xrd , Some localities are worse than others. Flambeau is now old enough for the scuzz to show up.
avatar Re: Flambeau Mine chalcocite
November 14, 2011 06:15PM
It seems to be an environmental problem more than anything else - I noticed that many of the chalcocites, bornites, etc, in the LA County Museum in Los Angeles suffered from this, but none of my specimens here in the UK do - even similar samples.

I wonder if it's related to airborne pollution rather than humidity/temperature?

Jolyon
avatar Re: Flambeau Mine chalcocite
November 14, 2011 06:19PM
    
Jolyon you are right.
avatar Re: Flambeau Mine chalcocite
November 14, 2011 06:58PM
A UCLA graduate student has studied decomposition products of sulfides among some specimens in the LA County museum collection. One of the (unpublished) conclusions is that pyrite disease is contagious within the same display case. In other words, there may appear to be a preference for some chalcocites to decompose while others are immune simply because some are displayed with rotting pyrites while others are not. As I recall another conclusion was that wood of the display case can retain the rot, infecting specimens in the case even after the rotted pyrites have been removed.

So I would be cautious about making any connections based on locality and susceptibility to decomposition without more thorough consideration of all the variables involved.
Re: Flambeau Mine chalcocite
November 14, 2011 09:03PM
    
I recently looked at my Flambeau chalcocite and noticed the same thing. It has not been in a cabinet but in white cotton box in a flat.
I also lost a large pyrite/marcasite nodule from France (i think). It was about 10 pounds and the size of a cantelope. Now it is a bag of crumbs and it is seems to be breaking down further. Soon it will be the size of flour. I put it in a zip lock bag, after giving it a bleach soak & distilled water rinse, when I noticed it deteriorating a couple of years ago. The bleach didn't stop it from deteriorating.

I have also noticed many of my Butte covellite, pyrites, chalcocites, and chalcopyrites start to "oxidize". Many I have had for over 20 years and have just noticed the discoloration start now. My best covellite no longer has any color to it. It is just black! And my others are loosing their color.

Rick
I know I am in my own little world, but everyone knows me here.
Re: Flambeau Mine chalcocite
November 14, 2011 10:17PM
Thanks for the info- nice to commiserate with others. But darn, the specimen was pretty pricey when I bought it in 1999.
avatar Re: Flambeau Mine chalcocite
November 14, 2011 10:20PM
Unfortunately, if you get brown scuzz on your chalcocites or bornites you probably should not collect them, as they're all likely to suffer in your environment.
avatar Re: Flambeau Mine chalcocite
November 14, 2011 11:12PM
I have heard about this and recall a paper by the Canadians regarding specimens kept in wooden display cabinets, especially ones made from oak. Something about the acids in the wood affecting mineral specimens if the wood is not treated and/or covered with a protective, polyurethane top coat.

All of my specimens are kept in painted birch display cabinets and I have not noticed any decomposition, including my Flambeau chalcocites.
Re: Flambeau Mine chalcocite
November 14, 2011 11:24PM
    
So what is in wood that would make sulfides to do this?

Rick
I know I am in my own little world, but everyone knows me here.
avatar Re: Flambeau Mine chalcocite
November 14, 2011 11:40PM
Let's not get too carried away about the wood connection.

Specimens in LA museum were stored in metal display cabinets using acid-free paper boxes, etc, but still suffered from scuzzing.

Oak cabinets should be avoided in particular as they are well-known to release more acetic and formic acid than other normal woods - but this is more of an issue for carbonates (see [en.wikipedia.org]) than for your sulphides.

Jolyon
avatar Re: Flambeau Mine chalcocite
November 15, 2011 11:06AM
    
I have often wondered to myself, if there was a microbial vector involved in sulfide decomposition disease
It anyone ever uncovers that culprit, if this is the vector, it might become a useful tool in non sulfur realease
treatment of sulphide ores...who knows.
avatar Re: Flambeau Mine chalcocite
November 15, 2011 11:10AM
Brown scuzz on copper sulfides is a totally different beast to the decomposition of pyrite etc ("pyrite disease")
Re: Flambeau Mine chalcocite
November 15, 2011 12:17PM
See also: [www.mindat.org] for the interaction between oak wood and calcite.
Re: Flambeau Mine chalcocite
November 15, 2011 02:10PM
    
Thanks Erik,

I have lots of oak trees in my yard I will have to make myself some Calclacite! But wait! I guess it wouldn't be a valid mineral species because of the new criteria established by the IMA. Damn!>:D<
Re: Flambeau Mine chalcocite
November 15, 2011 02:46PM
I shall repeat myself for the 10th time.

It's microbes that facilitate the alteration of sulfides. Over the millenia, they have produced every lovely and ugly secondary mineral in your collections. There would be no supergene alteration without them.

Kill the microbes and enjoy the stifling of the hated decomposition of, and coatings on your stored sulfides.

Sulfide metabolizing microbes such as thiobacillus inhabit every surface and pore of the planet including metal and wooden drawers as well as museum boxes and acid free labels.. And they are happy, sometimes, thousands of feet below the surface.

Kill them.

Janitor in a Drum, bactine, listerine, lysol etc.or some other "germicides" might help. Maybe lysol infused labels instead of acid free labels might be a better approach.

I highly recommend you all to obtain a copy of:

Reviews in Mineralogy MSA Volume 35 .

"Geomicrobiology"

Interactions Between Microbes and Minerals 1997 edited by Paul H. RIbbe.
avatar Re: Flambeau Mine chalcocite
November 15, 2011 03:01PM
Sorry Bart, for the 10th time you're wrong!

Jarosite on Mars does not mean there's life there.
Re: Flambeau Mine chalcocite
November 15, 2011 03:27PM
Sorry, Jolyon, but NASA thinks that jarosite on Mars does mean that there WAS life there !

Not that I have that much respect for NASA.

Find me a thiobacillus-free crumbled marcasite and I will accept your position.

Thiobacillus assays of soils are used by modern mining companies for base and precious metals prospecting.

A better sulfide pathfinder than iron concentration and sulfur concentration in a bulk ICP or XRF analysis. Lots of thiobacillus equals lots of pyrite instead of just lots of magnetite or gypsum.

On Earth, I'll admit..

Have you read Geomicrobiology? If not, I'll loan you my copy.
avatar Re: Flambeau Mine chalcocite
November 16, 2011 12:54AM
    
Supergene enrichment can occur in the absence of microbes. A study published in Geochimica et Cosmochimica Acta by Mathur et al. in 2005 showed that copper isotopes fractionate in different ways if the leaching occurs with or without the assistance of microbes. Secondly, all secondary minerals are not formed by microbes. As Enders et al. noted in a 2006 study conducted at Morenci Mine in Arizona and published in Economic Geology, “Even though the enriched blanket possesses viable sulfate-reducing bacteria, inorganic geochemical processes dominate supergene enrichment in this system. Comparing the annual carbon fixation occurring during biooxidation versus leaching, bacterial sulfate reduction could only fix between 0.2 and 1.1 percent of the copper being leached.” Lastly, jarosite on Mars indicates that water was present, but not necessarily life. I encourage you to read the paper published in Science by Tosca et al. in 2008 that discusses Martian fluid chemistry and concludes that Martian waters were usually inhospitable to life, at least the sort of microbial life we have on earth.

Nathalie Brandes
Professor of Geoscience
Re: Flambeau Mine chalcocite
November 19, 2011 02:49PM
I have noted something with respect to unstable sulphides, simply because I have always lived a rather spartan life - no central heating, temperature indoors typically not a lot higher than the ambient temperature outside except in cold winter weather when a fire's roaring in the grate. Now, in the 1990s I collected a suite of filiform pyrite micros from Prince Edward mine in the Dolgellau Gold-belt of North Wales. They were incredible under the SEM - taking micromounting to a hi-tec level - one of the photos won a MinMag competition back in 2001. See attached. Field of view is a fraction of a millimetre.

I still have a few specimens though had to dump some. Of the ones that were stored at another location - where the temperature was way, way higher - not one remains.

If I ever collect any more, I know exactly where I will store them: in the fridge. This may be a useful tip for anyone with sulphide specimens that they have concerns about.

Cheers - John
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