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Nickelskutterudite do you have proof?

Posted by Reiner Mielke  
Reiner Mielke February 13, 2009 10:30PM
In the exhaustive study done on the mineralogy of the Cobalt-Gowganda mining camps in 1971 ( The Silver-Arsenide Deposits of the Cobalt-Gowganda Region, Edited by L.G.Berry, Can Min. Vol.II, Part 1, 430p.) there was never any Nickelskutterudite found. All specimens were found to be Skutterudite that were intergrown with other nickel arsenides ( Nickeline, Rammelsbergite, and Pararammelsbergite). Although the crystals may look mono-minerallic and test positive for nickel, they cannot be considered to be Nickelskutterudite without XRD.
Recently there have come on the market specimens from Rusty Lake Mine in Leith Tp. labelled Nickelskutterudite. None of these have been XRD'd that I know of and of the samples tested from that mine in 1971 no Nickelskutterudite was found. I have personally collected at that same mine and found Skutterudite crystals to be relatively common, but considering the 1971 study, I would not have called then Nickelskutterudite without XRD.
This brings me to the question. "Has anyone XRD'd their samples of "Nickelskutterudite" from Cobalt-Gowganda?" If not then you should not be calling it Nickelskutterudite, rather Skutterudite. For example see:
Uwe Kolitsch February 14, 2009 06:25PM
Message sent.
Uwe Kolitsch February 16, 2009 07:39PM
Info from uploader:

However, the 1971 paper cited may well be out of date. I have seen several reputable dealers
selling Chloanthite and Nickelskutterudite from the Cobalt-Gondwana Area in the last 20 years.
One of these is Excalibur Minerals which is an internationally known supplier of rare species that
have been analytically confirmed and used as reference specimens for museums and universities.
They currently list specimens of Silver with Nicelskutterudite from the Cobalt-Gondwana area.
They have extensive and state of the art in-house analytical equipment to ensure the accuracy
of their identifications. The conclusion must therefore be that if L.G. Berry did not find any
Nickelskutterudite in his studies of Cobalt-Gondwana minerals prior to 1971, then other people
have found it since then.
Reiner Mielke February 18, 2009 01:07AM
Prior to the 1971 study it was thought that Nickelskutterudite (Chloanthite) was a common mineral in the Cobalt-Gowganda camp. All samples in the 1971 study proved to be Skutterudite. I checked the "CATALOGUE OF THE ONTARIO LOCALITIES REPRESENTED BY THE MINERAL COLLECTION OF THE ROYAL ONTARIO MUSEUM" 1977 by J.Satterly (OGS Misc.Paper 70) and at the time they had no Nickelskutterudite in their collection. I emailed George Robinson yesterday (Curator of the Seaman Mineral Museum and former Associate Curator of the National Museum of Canada) and he responded that he was not aware of the existence of any authenticated Nickelskutterudite from the Cobalt-Gowganda area.
There are probably still a lot of specimens out there that were collected prior to 1971 and are still labeled Chloanthite. The fact that a reputable dealer is selling it as such is irrelevant. There were may reputable mineralogists and museums in existence prior to 1971 and for whatever reason they mistakenly identified Skutterudite as Chloanthite probably is still in play today. It is possible ( but very unlikely) that some Nickelskutterudite has been found post 1971, but all specimens labeled as Nickelskutterudite are suspect until proven by XRD to be such.
Frank Keutsch February 18, 2009 02:47AM
I will do SEM/EDS analysis for free on this as I am interested. Clearly an analysis is the best way to clarify the situation.

If the specimen is close to endmember Co or Ni SEM/EDS is sufficient. If Co and Ni are comparable this method does not suffice as it is only semi-quantitative (which is just a nice way of saying not quantitative), but it could prove useful.

Reiner Mielke February 18, 2009 02:38PM
Thank you Frank for your generous offer.
I hope that people with "Nickelskutterudite" will take you up on the offer. I personally have no Nickelskutterudite in my collection. I have lots of what I assume is Skutterudite, but I don't imagine you want to go on a hunt for Nickelskutterudite. If you do, let me know and I will send you a bunch of samples. According to the 1971 study most of the Skutterudite has a Nickel:Cobalt ratio of less than 1:3. However, there were a few analyses as high 2:3. Iron is also a significant component in the Skutterudite and is found in concentrations as high as the nickel. Hopefully you will be able to help resolve this issue. I am hoping that some Nickelskutterudite will turn up as it will make collecting there more interesting.

Reiner Mielke March 13, 2009 06:24PM
I sent out a sample for analysis of what has recently appeared on the market as nickel skutterudite from the Rusty Lake Mine, Leith Twp. ON ( part of the Cobalt camp). The XRD and EDS came back Skutterudite with no Ni. The analyses where performed by George Robinson and the sample was provided by David Joyce. As such, I repeat; there is no confirmed nickel skutterudite from Cobalt-Gowganda and if someone claims they have some, then I suggest that they are incorrect, unless they have XRD data to prove otherwise.

Uwe Kolitsch March 13, 2009 07:42PM
Status changed to unconfirmed; comment added in the comments field.
Tony Nikischer February 22, 2012 09:14PM
And proof is still elusive: an old and rather large specimen labeled as "Nickelskutterudite" from Cobalt was recently obtained from the A.E. Seaman Mineral Museum. Analyses conducted here in our lab showed Ni:Co ratio danced around 1:3, clearly identifying the material as skutterudite, not nickelskutterudite, despite the famous label.

Tony Nikischer
Excalibur Mineral Corp.
Reiner Mielke February 23, 2012 01:50AM
The problem is that early on it was thought that Chloanthite was a common mineral in Cobalt so all the old labels still have that name. It was later discovered that they were intergrowths of Skutterudite and Ni arsenides.
Bart Cannon February 23, 2012 11:44PM
I have checked "nickel skutterudite" from the Alhambra Mine, Grants, New Mexico. Seemed OK via EDS.

Shiny xls occur on silver.

Reiner Mielke February 24, 2012 01:01AM
EDS will work as long as the sample is at the far end of the series, but it gets pretty iffy when Ni:Co gets anywhere near 1:1. I think a lot of it would require quantitative analysis.
Don Saathoff February 24, 2012 02:53AM
At the Alhambra, Blackhawk, and Rose mines, Blackhawk Dist., Grant Co., NM, the nickleskutterudite has been studied repeatedly since Hillebrand in 1889. All studies have confirmed nickleskutterudite. The list of references is somewhat extensive or I'd post them here. They can be found in Northrop's Minerals of New Mexico, Third edition, revised by LaBruzza.

David Von Bargen February 24, 2012 12:28PM
The Black Hawk district has very little cobalt in the ore. (although it is concentrated more as you go from niccolite to nickel skutterudite and the sulfarsenides)
Frank Keutsch February 24, 2012 02:19PM
Verified nickelskutterudite exists from various localities. I think Reiner is saying that he knows of no verified sample from Cobalt.

Reiner Mielke February 24, 2012 02:37PM
What I am saying is you have to very cautious about calling something nickel-skutterudite to avoid a situation like occurred in the Cobalt-camp.
Also it took me three tries to find a nickel-skutterudite sample from Germany, the first two turned out to be skutterudite even though they were labeled chloanthite, so you can not trust the labels.
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