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Gap Nickel Mine

Posted by Greg Kokolus  
Greg Kokolus May 29, 2012 06:02PM
This past weekend I went on a club sponsored trip to the Gap Nickel mine here in PA. I've also gone last year to the same location. The collecting site with the tailings is largely a brownfield due to the high acidity. It was trenched last year so there is a fair amount of material exposed on the surface as well in the walls of the trenches. The most common minerals seem to be Pyrite, Siderite, Chalcopyrite and Pyrrhotite.
Additional metallics referenced include Pendlandite and the holy grail Millerite. I currently have material soaking in Iron out to try to devine what it is that I have. According to the sources I read, it was suggested that Millerite was the source of the Nickel for the years that they specifically processed the ore during the late 1800's. What is a curiosity to me is that if in fact that is correct, why you don't see as much as a shard of the material on the dumps. I'm not refered to the acicular variety of xls, but even the more massive seam material like shown on the Betts site. I know that collectors have been over the dumps for decades, but given the ineffective cobbing of material before processing I would expect at least something. I looked at the photos of Millerite here on the site and the closest massive material I found is from Sudbury Canada.That is ironic given that I have seen a theory that suggests the Nickel deposits at both locations are chemically identical and originally came from a large meteorite that broke apart with some landing in Gap and the rest in Sudbury. Normally I am very good at being able to tell metallics apart, but the specimens I have are seemingly such an amalgam to blur lines. In fact I'm wondering that maybe some of the massive brassy material I've seen before cleaning is actually massive Millerite that I mistakenly passed off as Pyrite. One collector has suggested that you don't see the Millerite on the dumps because it has decayed since coming to the surface.To add further confusion I've also seen Penlandite suggested as a primary source of Nickel as well. In our PA guides there is mention in the Smith book, but they show it as a slide with a cross section of the mineral. If you have collected this site or can help with my understanding of the relationship of all these minerals, I'd be interested in hearing your thoughts.
Greg Kokolus
Peter Haas May 30, 2012 01:24AM
When you're digging on such dumps, always keep in mind that nickel ions are strongly carcinogenic, and thus all nickel compounds that are at least somewhat soluble are very hazardous materials.
Reiner Mielke May 30, 2012 11:44AM
It is most likely that there is fine grained pentlandite in the pyrrhotite, in which case you are not likely going to see it unless you do a polished section.
Greg Kokolus May 30, 2012 03:59PM
Gap Nickel dumps have long been visited by collectors here in PA.
Would you please explain further what you are talking about?
Greg Kokolus
Tim Jokela Jr May 30, 2012 04:38PM
The brilliant golden luster, and the remarkably perfect cleavage, are dead giveaways for massive, cleavable millerite. Easily distinguished from other cu-ni minerals, even in tiny amounts if you've got good eyes. You might consider getting a polished section made and analyzed. Good luck with the fun sulfides!
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