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Identity HelpPyrite, comments please.

1st Sep 2017 03:01 UTCGreg Dainty

I recently acquired a couple of these pyrite specimen seen in the attached pics, size is 23 x 9 x 7mm. The only location given was "China". Could anybody comment on a location, for them and any comment on the form would be welcome, Im not familiar with the form, and looking closely at them they dont appear to be broken from a pyrite ball, and have no obvious contact points. Thanks.

6th Sep 2017 02:22 UTCDennis McCoy

Possibly a psuedomorph?

6th Sep 2017 07:18 UTCUwe Ludwig

Are you sure that this is Pyrite? Markasite or Arsenopyrite should be an option.

Rgds.

Uwe Ludwig

7th Sep 2017 18:48 UTCEd Clopton 🌟 Expert

I suspect this is a small sector of a spherical concretion that broke apart, revealing its radial structure.

7th Sep 2017 19:03 UTCRob Woodside 🌟 Manager

Ed has nailed it.

7th Sep 2017 23:48 UTCPhil Richardson

Greg,

As Ed stated, and Rob supported, my opinion is similar. At a past tailgating mineral show, another supplier was there with a 'different' batch of spherical Chinese 'pyrites'. We had a debate as to whether it was pyrite or marcasite. So, we bought several, and had Michael Shannon crack them with his Zuber trimmer. Both spherical crystal clusters broke apart creating radial sections similar to what you have pictured. The radial sections show the 'cubic' section on the exterior terminus, have radial alignment as yours, broke very cleanly along those radial lines, and a silver/golden coloration. We concluded that these were marcasite clusters.

8th Sep 2017 00:37 UTCDonald B Peck Expert

Ed's explanation is very reasonable. Several years ago, spherical iron sulfides were being collected from the clay pits at Sayerville, NJ. They were bright, brass yellow with often square "terminations" covering the surface. They looked like pyrite roses and sizes to four inches were not uncommon. They were beautiful specimens -- difficult to dig out of the wet white clay. Over the years, they disintegrated, becoming a pile of greenish gray white powder.

Originally we thought that they were pyrite. When they disintigrated, my thinking went to marcasite. Has anyone done a definitive study on whether "pyrite disease" actually attacks pyrite, or is limited to marcasite?

8th Sep 2017 04:39 UTCEd Clopton 🌟 Expert

My experience (admittedly anecdotal) with a number of specimens personally collected at the Mt. Carroll quarry, Carroll County, Illinois (https://www.mindat.org/loc-221996.html) is that, contrary to what one would expect, some pyrite from that locality seems more susceptible to "pyrite disease" than most of the marcasite. All of my Mt. Carroll marcasite specimens are as good as new more than 30 years after collecting, but some apparently solid pyrite specimens have deteriorated. Both species are abundant at the locality (or were 30 years ago), and most can be readily identified by crystal habit as either pyrite or marcasite, so basic ID is not in question. I haven't had anything analyzed to see whether it's actually traces of marcasite that are making what look like pure pyrite specimens deteriorate, or whether either species is present as a pseudomorph after the other (although I really doubt that that is the case, given the simple mineralogy of the site and its location on the very fringe of a low-temperature Mississippi Valley type deposit). Not a definitive study, but that's my empirical experience.

9th Sep 2017 01:59 UTCJohn Oostenryk

Aloha Don Peck! Hope all is well on your side of the state! :)

Hello Ed!

Glad to see more Carroll Co Quarry stuff in archive. Nice collecting!

So YOU were the guy who was before me (by 20 years?) to L&D #13 rip rap. Weathering had mostly obscured your 'tracks', but I thought a couple times someone had broke some boulders? Ha, I WAS seeing that! Stories for another time/thread!

We really must talk sometime, please! Will PM you in near future with contact info?! :)

I too got some neat thumb stuff over period of years, years back (2006-2010?). Learned a lot there-regarding extraction processes and later prep!!!

I hate to say again... REALLY must start entering my finds here... Not soon at present though. Projects elsewhere now...

I would agree with your comment- ID was easy due to morphology.

However, I found even odds on survival/decay of iron sulfides. Yes - cleaving on the pyrite but also marcasite.

It was material there that I realized Reiner's idea on oil soak would fix that decomposition 'disease'.

There is natural hydrocarbon in the formation in places- I'm confident due to specimen placement with it- certainly a positive factor.

Did you see oils when FRESH in rock at L&D #13 - or was it always more Tar sand/tar/bitumin?

I popped lil vugs a couple times in breaking rocks and had sweet light crude ooze out!

Best Regards!

9th Sep 2017 17:02 UTCRob Woodside 🌟 Manager

The square ends show that this xllized as pyrite. The yellow colour argues for it still being pyrite. Marcasite is green!!! However we should be looking at the colour of a fresh surface to be certain it hasn't pseudoed to marcasite.

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