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Bornite, chalcopyrite, or?

Posted by SharonF  
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SharonF December 07, 2017 09:46PM
Hi,
Can anyone tell me whether this is bornite, chalcopyrite or something else?

Acid washed or not?

It was labelled covellite but I don't think it is.

Quite heavy and has a grey streak.

Thanks in advance.



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Matt Neuzil December 07, 2017 10:09PM
It looks like a rather solid chunk. Calling it heavy doesn't do much to help solve your question. Look up how to test specific gravity and get an accurate number and that will help. Scratch test has been performed? Hardness test? You need to perform some tests. I photo alone not solve this.
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SharonF December 07, 2017 10:19PM
I'm getting a specific gravity of 4.58, not sure my scales are super accurate but doesn't seem to quite fit either according to my mineral books.
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SharonF December 07, 2017 10:20PM
Also trying not to scratch if possible as it's for someone else.
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SharonF December 07, 2017 10:23PM


Streak
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SharonF December 07, 2017 10:58PM
It is easy to scratch parts off with my finger nail, but unsure if it's a coating.

Tried a fine point steel nail file, which does scratch it, and it appears to look the same underneath and the scratch is not really noticeable.

You can see bits that have crumbled off in the streak picture.



Edited 1 time(s). Last edit at 12/07/2017 11:01PM by SharonF.
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Paul Brandes December 08, 2017 12:19AM
Why do you believe it's not Covellite?
The appearance, streak, and SG certainly match much closer to Covellite than your other options.
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Reiner Mielke December 08, 2017 12:38AM
Covellite has a perfect cleavage and I see none. Also the sample does not look pure, so S.G. could be lower than it should. Looks more like chalcocite or bornite to me. A good clear closeup is needed.
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SharonF December 08, 2017 08:25AM
Paul Brandes Wrote:
-------------------------------------------------------
> Why do you believe it's not Covellite?
> The appearance, streak, and SG certainly match
> much closer to Covellite than your other options.

I generally stick to what I can confidently identify myself when buying. In this case I didn't.



Edited 2 time(s). Last edit at 12/08/2017 12:25PM by SharonF.
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SharonF December 08, 2017 09:11AM
I only have a phone camera unfortunately.





Edited 1 time(s). Last edit at 12/08/2017 09:15AM by SharonF.
open | download - IMG_7468.PNG (1 MB)
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Reiner Mielke December 08, 2017 10:36AM
For sure not covellite, looks like bornite to me. What color is it if you break off a tiny piece. Untarnished bornite is brown.
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SharonF December 08, 2017 10:58AM
I don't really want to break it, not sure how to go about getting a small piece off without totally trashing it?

We've got some sunlight now so here's some better pictures.




If it's bornite is the colour treated as all my books seem to suggest it would tarnish to a purplish iridescence if natural?

Edited to add it does look purplish in places.



Edited 1 time(s). Last edit at 12/08/2017 11:08AM by SharonF.
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SharonF December 08, 2017 11:06AM
Searching images of tarnished bornite I am finding similar images.

So peacock ore is another name for tarnished bornite? But then there's a lot of information about that says most of what is sold as peacock ore is actually coated chalcopyrite. So that's what I'm trying to work out really?
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SharonF December 08, 2017 11:25AM
It looks a lot like chalcocite pictures I'm finding now.
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Reiner Mielke December 08, 2017 11:34AM
Bornite will tarnish blue in air ( within a week) without any special treatment, chalcopyrite on the other hand must be artificially acid treated.The simplest way is to chip off a tiny piece and observe the color. Chalcopyrite will be a bright gold color and bornite brown. I can see a couple places you could easily break off a tiny piece with a pair of end or side cutters that would not significantly damage the specimen.
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SharonF December 08, 2017 11:50AM
Looks bright gold to me, so chalcopyrite?

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Wayne Corwin December 08, 2017 12:08PM
looks like it, yes.
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Rolf Luetcke December 08, 2017 12:36PM
Sharon,
Big problem is there is just a ton of the artificially tarnished material out there, they pretty much use chalcopyrite for this and blue is the main color it turns.
I believe you did it right with removing the tiny piece.
The artificial material is so common out there that the piece doesn't have a lot of value, I have sold pieces like yours for a buck. Nobody asked location and if there is none, then I assume also the artificially tarnished chalcopyrite.
Still a pretty little piece but truly not much value.
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Paul Brandes December 08, 2017 12:53PM
Now that you have better photos showing the blue/purple/green iridescence and the gold coloured chip off the corner, chalcopyrite seems likely.
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SharonF December 08, 2017 01:01PM
Thanks all, I did have a hunch this was going to be the case after checking my mineral books and other sources. I wasn't confident my scales are accurate enough for SG testing.

I only had one other piece to compare it to, which is a pink and gold piece I've had for years. I knew that was artificially treated as the seller was clear about it. That has lost a lot of the tarnish over the years and looks brown where the tarnish has come off. However, when I used my cutters in the old piece it comes up exactly the same as this piece.

I'll speak to the seller.
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SharonF December 08, 2017 01:17PM
I paid £8 (approximately $10) for this!
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Peter Keller December 08, 2017 01:53PM
Sharon, I agree with Reiner and would be 99% sure it is massive bornite from your photos. Sometimes you can get small patches of golden chalcopyrite occuring in the bornite as they often occur together. Those purplish hues are a give away. Almost certain it's not covellite. It is also completely natural and has not been treated. The pretty coloured "peacock ore" sold in bulk everywhere is acid treated chalcopyrite not bornite. No it's certainly not worth more than the price you paid for it, especially without reliable locality information.
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Philippe Virlet December 08, 2017 03:25PM
This looks like bornite as we can find in Katanga (Kipushi, Kambove ...)...
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Reiner Mielke December 08, 2017 03:34PM
The color of the broken surface looks brownish on my monitor rather than golden so I would say it is bornite. If you want to be sure wait for a few days and you should see it start to slowly turn blue. Chalcopyrite will not do that. Might take a couple weeks to get as blue as the rest of the piece.
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SharonF December 08, 2017 03:50PM
Here's a slightly better picture, definitely gold. I will wait and see whether it turns colour.

I've spoken to the seller and he did say he bought peacock ore from the same supplier at the same time but it was completely different, and neither of us had seen peacock ore quite this shade. He's happy to refund me either way, but I'll be happy if it turns out to be bornite.

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Dale Foster December 08, 2017 03:58PM
Got to admit I agree with Reiner, to my eye as well this looks brownish rather than the golden of Chalcopyrite:



Your specimen does look more like Bornite based upon the pictures you have supplied.
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SharonF December 08, 2017 04:23PM
Thanks Dale,

The chalcopyrite in your picture looks a similar colour to my pyrite. If that's the case this is definitely a darker colour, almost like rose gold.
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SharonF December 08, 2017 04:29PM
Philippe Virlet Wrote:
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> This looks like bornite as we can find in Katanga
> (Kipushi, Kambove ...)...

Phillipe, thank you for mentioning a location I think you are correct. My search brought up this page on here and the 2nd picture is very much what it looks like.

https://www.mindat.org/locentry-22846.html
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Donald B Peck December 08, 2017 04:49PM
Sharon, I think you can trust your scale and the SpG you determined. If your specimen is bornite (which I think is probable), the SpG is a bit low, but if there is much chalcopyrite in there, that is what it should be. Your determination for covellite is very slightly below the low end for covellite ( and is possible, given the inclusion of the chalcopyrite). The streak appears to fit either bornite or covellite. If the specimen is a solid chunk, and is not flakey, I would go with bornite. If it is flakey, it may be covellite.
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SharonF December 08, 2017 05:06PM
Donald,
The SpG is throwing me. Could it have some reneirite as that's closer and commonly associated from the same mine? I'd say it's more solid than flakey.
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Reiner Mielke December 08, 2017 05:52PM
Like I said before the SG is probably low because it is not pure. As for reneirite don't even think about it unless you want to spend a lot of money on analysis. Also you cannot determine the locality based on pictures as there are hundreds of localities that could produce something that looks like what you have.
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SharonF December 08, 2017 07:40PM
Ok, thanks Reiner. I was only really thinking about locality because it was only by searching for bornite from that locality through Phillipe mentioning it that led me to a picture that looks more like it than anything else I've seen.
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Donald B Peck December 09, 2017 02:51AM
Sharon, Chalcopyrite has a lower SpG than bornite. If there is any chalcopyrite in bornite, it will make the overall SpG lower than that for pure bornite. Is the sample flakey or not? The reason I am asking is that covellite has a pronounced perfect cleavage while bornite has none. in this respect covellite resembles a mica. If small flakes come off your specimen it could be a fairly massive sample of covellite.
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SharonF December 11, 2017 11:00AM
Thanks Donald, it's not flakey or mica like at all so I think it's probably a mixture of bornite and chalcopyrite.
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