FMF - Friends of Minerals Forum, discussion and message board

[Laurent R-C]

Hello all,
It is my first time posting here, so please spare some patience for me!

I’ve got this fun (but really unassuming until you pick it up) rock bought at an Ontario university geology department fundraiser sale a couple years ago.

It is extremely dense, weighs 86 grams - a lot for such a small rock.
It has a grey-gold metallic sheen with quartz on the edge.
It has a grey metallic streak, initially bubbles and only partially dissolves under platinum test solution.
The full specimen has a specific gravity of around 6.14 (very very roughly), but the measurement includes a significant amount of matrix
The metal ore is quite hard, I couldn't do a proper scratch test, but it did happily scratch my ceramic touchstone (annoyingly...).

To satisfy my curiosity, I had a local gold smelter put it under their XRF machine for me, the output is in the last image, but the standout is the 10% gold and 45% Iridium results.

These latter, and some googling (as well as a reddit post) have pushed me towards my initial conclusion.


I'm a "I like cool rocks" guy, but I'm not a "I want to keep a potentially very valuable hunk of metal in rock form in my garage" type of guy. What can I do with this?

Looking forwards to suggestions and your knowledge!

LRC

[alfredo]

Forget the XRF, which is obviously not properly calibrated for the type of material you have. Best first measure the density, which doesn't need any high-tech equipment other than accurate weight measurements.

At first glance, you might have nickeline, a nickel-arsenic mineral, which feels pretty heavy since its density is almost 7.8 - You can compare with photos of Canadian nickeline here: https://www.mindat.org/gallery.php?loctxt=canada&min=2901

[Peter Lemkin]

This forum is NOT about values of minerals - no matter what they are and what they are worth or the poster thinks they are worth. Your not very subtle hint that you want to sell this for the highest price and ask us to tell you how best to go about that is not appropriate. A chunk of Au/Ir that size [and that 'grade'] has, to my knowledge, never been found and would only be [were it really that] human made. https://www.mindat.org/gm/2045 https://www.mindat.org/gallery.php?min=2045

I think you are on the wrong track, and will be quite disappointed with the truth - and we can not help you monetize whatever it is. If you keep on the value 'track' the moderators will terminate the thread. If you want to get help in knowing what it is, perhaps we can help. We are the 'kind of guys and gals' that are interested in knowing as much as we can about natural minerals and crystals without discussions of value and commercialization of them - that can be found on other websites.

[Laurent R-C]

Well that's quite an aggressive way to treat first time posters - especially one who was hoping from a touch of patience from the experts, but nevertheless, my goal, before even thinking about anything else, is figuring out what the heck I have in front of me, so let's have at it ignoring any misguided initial value questions!

With regards to the XRF - it is quite possible that it isn't calibrated for the analysis of "random rocks" but my instinct is that it should be quite well calibrated for precious metals, that is after all its business and iridium and gold being two of them. - is that instinct wrong?

Nickeline is an interesting possibility, though my piece is grey, without any reddish tinge - If you read through my first message, I did do an SG test - it does align with the possibility of Nickeline at first glance, but the amount of matrix on this piece is significant. Given it would have a high nickel content, is it likely the XRF might have missed it completely?
I do have a set of gold test acids, I'm sure its not exactly a scientifically excellent test, but I know that nickel reacting with 14k test (fuming nitric) characteristically tests to a green colour with vigorous bubbling. So, I ran a comparison between a 99.9% pure nickel Canadian nickel from the 70's and the specimen in question here. The rock bubbles only slightly, while the nickel was attacked quite vigorously by the acid. Wiping with a paper towel left green staining from the coin, but only a colourless/gray residue from the rock.


What should be next in the list of tests I could go for?

[Joseph DOliveira]

Did you get a location for the specimen when you purchased it, that would be a big help?

[Laurent R-C]

Unfortunately not,
The sale was being run by some geology students who had for all practical intents and purposes dumped out every specimen collected in the prior 50 years onto a classroom floor and were selling everything for between 25 cents and 5$. Some had hand scribbled ID cards from decades past, but this one did not.

An additional note - Nickeline should have a reddish streak from what I see on the internet, mine is silver grey, similar to that from a sterling silver ring, but duller and with less shine.

What's next on my test list!

[Joseph DOliveira]

Just looking at the picture, I would guess that it may be from the Cobalt area of Ontario. The light green oxidation on the outside would indicate a nickel arsenide (nickeline, rammelsbergite) which are often found in combination in the Cobalt area ores. Tons of this material was left on the waste piles when the mines were closed and the area has been heavily collected over the last 50 years.

Obviously I'm making assumptions but that is what the image indicated to me and I've seen a lot of cobalt material over the years..

Cheers,
Joe

[Laurent R-C]

Very interesting!
Rammelsbergite seems to be possibly closer than Nickeline from looking at the Mindat specimen - at least colour wise and streak wise we'd be closer to what I have,
But I can't shake the XRF outputs, and my non scientific "nickel test".
Is there anything I can do to help our identification along?

Thanks a ton!

LRC

[Bob Carnein]

Hi, Laurent, A number of mineral dealers do X-ray diffraction testing for a fee that isn't too expensive (I don't think this Forum is a place for me to list examples, but if you PM me, I can make one or two suggestions). Also, you might try the university where you purchased the specimen. The least they could do is give you a reasonable ID.

[Laurent R-C]

That's a good plan - I think I'll follow up on the University XRF suggestion.
Is there a reason to expect significantly different results from those offered by the gold buyer's machine? It was a desktop model, but I know little about it otherwise!

[Bob Carnein]

I'm suggesting XRD, not XRF. XRD identifies specific minerals rather than chemical constituents.

[Peter Lemkin]

[alfredo]

Sorry, Laurent, I completely missed that you'd already given the specific gravity in your first post.

As for the colors, in the photos the metallic parts look pinkish to me and the surface alteration looks greenish, but those colors might be just artifacts of the lighting or reflections from the background. You might get truer colors by taking the photos outdoors in daylight, on a neutral white base.

Regarding XRF, over the years I've seen so many impossibly screwy results from XRF tests on minerals that I generally distrust them. Many things can go wrong. The suggestion others have made to get XRD done on it is the best.

[Laurent R-C]

I've reached out to a university acquaintance with access to a lab - hopefully we can get it in there soon for a more decisive answer!
In the meantime, as long as I still have the rock under hand, I'm open to any test you can think of!
Thanks

[Peter Lemkin]

https://www.mineral-forum.com/message-board/viewtopic.php?p=19487#19487