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I am looking for decayed pyrite and marcasite specimens for research
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Trudy Bolin




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PostPosted: May 31, 2011 15:51    Post subject: I am looking for decayed pyrite and marcasite specimens for research  

Popping sounds? I haven't heard of that before. That's interesting.

I am not a mineral collector, but I look at metal sulfide transformations in fossil fuels. I have been interested in how pyrite and marcasite (polymorphs differing by crystal structure) act in a coal matrix for some time now, and my search for differences in how the two minerals behave led me to mineral collectors.

I'm thinking that if there was a transformation of marcasite to pyrite (which can happen under the right conditions) then the mismatch of the crystal structures of the calcite and the incident pyrite or marcasite could lead to separation. But I've never heard of popping sounds. Shullsberg marcasite specimens are notoriously unstable, while pyrite specimens from the same area are very stable. I would also caution against determining the identity of marcasite and pyrite by appearance (habit, I think?), as I ordered some marcasite from a chemical company, and while they appeared to look like marcasite crystals, powder diffraction determined it was actually 100% pyrite. That "marcasite" (pyrite) sample is also behaving differently in a humid environment than the cubic pyrite I ordered.

I actually took the liberty of searching about 163 mines that had pyrite in them in LaFayette County, WI (mindat.org) and found that 148 of those mines had ONLY calcite, dolomite, pyrite, quartz, and sphalerite. The other 15 had other things in them, with 13 out of that 15 having both pyrite and marcasite, and 2 having marcasite and other minerals and no pyrite. One of the 13 was Shullsberg, with a zoo of minerals. Not sure what to make of the numbers, but its interesting.

Having said that, I am looking for decayed pyrite and marcasite specimens. I would like to look at them and see what's actually there using spectroscopy. It may give me a clue about what is causing the instabilities. I'm especially interested in samples that can be tied to a specific locality and conditions under which they were stored.
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Jordi Fabre
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PostPosted: Jun 04, 2011 09:52    Post subject: Re: I am looking for decayed pyrite and marcasite specimens for research  

Surprisingly this very interesting post don't get answered yet. Trying to promote it I moved to this new, individual, thread with the hope to start a discussion about the topic proposed by Trudy, or at least to help him to collect some decayed Pyirite & Marcasite for his research.
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Darryl




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PostPosted: Jun 04, 2011 11:37    Post subject: Re: I am looking for decayed pyrite and marcasite specimens for research  

Hello Trudy,

Would crystals in coal and carbonaceous shale be of any use to you? The crystals range from sub mm to mm and occur in loose clusters ranging in size from mm to cm. I haven't looked closely at them for several years but as I remember the ones I have are typical pyrite xl forms but very dull if not brassy green and I think I can get some of the typical cox-comb marcasite forms from a friend if you would like them.

The crystals are from Triassic lake and stream sediments which have local pods (several meters across and a meter or so thick) of coal shale & clay. The crystals are typically found inside soft chunks of coal and/or clay. The climate where they are found is typically arid to semi-arid w/ some localities bieng in deep stream channels which are well shaded and more humid. There are frequently abundant selenite gypsum blades and sulfur found in the same beds and some calcite veins occur in at least one pod that I know of.

Since being recovered some decades ago the crystals have been stored on shelves and in boxes in homes with refrigerated air condidtioning and average humidities of 30-40% for 6-9 months of the year and from 10-20% during the other 3-6 months.

Darryl
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Tracy




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PostPosted: Jun 04, 2011 13:52    Post subject: Re: I am looking for decayed pyrite and marcasite specimens for research  

Hi Trudy -

I still have the decomposing "pinecone" pyrite specimen about which I posted (it's too pretty to just throw away, Jordi - what can I say...only now it's in a box). And being a Fabre specimen the locality info is quite reliable. ;-) I'd be glad to donate it to you. Do you want the bits that broke off or the entire specimen? I had another pyrite, a ball from China, which decomposed but I'm pretty certain I tossed that one, along with the remnants of a "sun dollar." It would not surprise me if humidity was the main cause of my pyrite specimens' demise, still.I'd be very interested to learn of your findings.

- Tracy

ps Jordi, the "hairsprayed" sun dollar which you told me how to preserve looks as good as the day I got it. Thanks!

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Jordi Fabre
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PostPosted: Jun 04, 2011 15:27    Post subject: Re: I am looking for decayed pyrite and marcasite specimens for research  

Andrew Sicree wrote:

Hello Trudy,

Can you tell me what techniques you plan to use to analyze the pyrite/marcasite?

I can give you some interesting samples. Please contact me at the
address below.

Sincerely,

Andrew

Andrew A. Sicree,
(Ph.D. geochemistry and mineralogy)
671 Boalsburg Road
Boalsburg, PA 16827
(814) 867-6263
sicree(at)verizon(dot)net


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mmauthner




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PostPosted: Jun 05, 2011 11:54    Post subject: Re: I am looking for decayed pyrite and marcasite specimens for research  

Hi Trudy,

Just saw this post...what timing!

I am currently involved in a project going through a museum's collection to determine specimens for deaccession using the museum's current, revised collection mandate. Among the items for immediate deaccession are many decomposed sulfides, mostly pyrite & marcasite. If you would like these, I am sure I can get them to you. Please contact me via private message if you are interested. I would, of course, only provide those with reliable locality information. (By the way, included is a specimen---heartrendingly and formerly beautiful---of a pyrite pseudomorph after marcasite from the famous pyrite locality, the Nanisivik Mine in the Canadian Arctic. This specimen still has areas that are doomed but somewhat intact and may in fact have both species present for study.)

Cheers,
Mark
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Trudy Bolin




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PostPosted: Jun 06, 2011 14:37    Post subject: Re: I am looking for decayed pyrite and marcasite specimens for research  

Hi. I can't write private messages yet, as I just joined the forum.

Darryl, I would like very much to see the coal and shale samples, with the pyrite and the marcasite. Certain clays are a suspected catalyst for the decay process.

Tracy, yes if you want to donate your pinecone that would be nice. The pieces that broke off are fine, as I don't want to further damage a specimen that you seem quite attached to. (I have to grind the material up.)

Andrew, I will go ahead and contact you at the address given.

I'll wait a few more days until I can send private messages and then do so.

Thanks! Trudy.
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mmauthner




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PostPosted: Jun 06, 2011 14:58    Post subject: Re: I am looking for decayed pyrite and marcasite specimens for research  

You can email me at mmauthner(at)gmail(dot)com if you want to.

Mark
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Darryl




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PostPosted: Jun 06, 2011 15:54    Post subject: Re: I am looking for decayed pyrite and marcasite specimens for research  

Hello Trudy,

I am on a drilling rig now and will be here for the next 7-10 days so won't have a chance to look at my samples or go to the field to get new ones until I get home.

You may write me at maddox7803 (at) yahoo (dot) com if you wish. I have photos at home of some of the localities so I can go get "fresh" badly weathered samples if you want a type I don't happen to have at home. I just checked with a friend and he said he thought most of his samples had completly fallen apart but was up for a field trip to see what can be found. He did say one of our classic collecting localities was barren the last time he was there (a few weeks ago) but there are so manyothers that one being barren just means 1 less we have to check. I want to point out that to my knowledge no one has ever collected a "fresh" sample from any of these localities. They are all badly discolored. As for hardness as an indicator of degree of oxidation or re-crystallization or other form of decay I can't say because I have no way to determine harndness to the degree of precision I would think such information would require. I am pretty sure no one has ever done any other form of analytical work on them simply because no cared.

This is a good excuse to get out and see how many kinds I can find. I will check with some of my other friends to see what information and/or data they may have.

Darryl
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Jordi Fabre
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PostPosted: Jun 06, 2011 16:00    Post subject: Re: I am looking for decayed pyrite and marcasite specimens for research  

Trudy Bolin wrote:

Hi. I can't write private messages yet, as I just joined the forum.


Mark (and others), please note that although currently Trudy can't send PM, he can receive and answer PM if some FMFer send it to him.
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arturo shaw




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PostPosted: Jun 07, 2011 01:32    Post subject: Re: I am looking for decayed pyrite and marcasite specimens for research  

Hello

In the Spanish side of the Forum there has been a thread on the decay of Galena (Pyrite is aldo mentioned there) and a possible treatment with.... antibiotics. I know that the person who started the thread will do some research on the subject.... one day. He is a biologist but he is also very busy with other obligations (or at least that's what he says :-) ).

Text is in Spanish but there are several translators out there.

The link: https://www.foro-minerales.com/forum/viewtopic.php?p=41394#41394

Cheers

Arturo
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Trudy Bolin




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PostPosted: Jun 22, 2011 16:07    Post subject: Re: I am looking for decayed pyrite and marcasite specimens for research  

Hi. I have been offered some samples of decayed pyrite and marcasite. Thanks! I eagerly await them, as the more statistics I have the better. In the meantime, I have also obtained some decayed specimens from Wisconsin. I see what is meant by "decay".

I haven't been able to use spectroscopy on all of them yet, but have gotten a chance to put some of them under a microscope. I'm thinking that two of the main forms of iron sulfate present, from the literature and comparing images on mindat.org to my sample, may be szomolnokite and rozenite. Other suspect iron sulfates that could be present (from searching the literature): roemerite, rhomboclase, coquimbite, and paracoquimbite. Melanterite is also noted as a decay product. If pyrite is mixed with kaolinite (clay) then there could be copiapite, halotrichite, and alunogen.

These are not terribly common mineral specimens, and haven't had much luck with finding specimens for sale. Would anyone know where I could get some or all of these minerals? I am eventually going to get to a point where I will try to fit my data with combinations of these compounds.

Whatever the minerals are, some are definitely soluable in water. I have a piece of the specimen on a white paper towel, and it turned yellow when I applied a few drops of water. If there were sulfuric acid around, I would have expected the paper to further deteoriate, but it hasn't showed signs yet. It may be that the acid is too dilute now.

On another note, I did have a chance to look at some slightly decayed marcasite on galena (have to diffraction to confirm the phase) and I am definitely seeing sulfide and sulfate with spectroscopy. The marcasite on this specimen is poking out from the galena in one spot and the area around it is whitish-yellow. It looks like it may be a combination of two sulfates: some sort of iron sulfate (not a shock) and what looks suspiciously like lead sulfate. I have an old publication from Mining World that did a bench-top study of the rate of oxidation of sulfides. The year is 1910 (H. A. Buehler and V, H, Gottschalk.) They noted that when pyrite or marcasite is mixed with other metal sulfides, the other metal sulfides tend to oxidize much more quickly. So lead sulfate is not such an odd finding.

Thanks! Trudy.
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GneissWare




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PostPosted: Jun 22, 2011 17:42    Post subject: Re: I am looking for decayed pyrite and marcasite specimens for research  

Szomolnokite was analyzed and identified at the Miekle mine (Carlin Trend Nevada), generally as a dark core in some of the botryoidal pyrites found there. I also recall it as part of an iron sulfate gel in some specimens. These pyrites were also found with the Millerite from the Miekle. My recollection is they did a very good job eating through the cardboard and paper storage boxes. If you PM me with an address, I'll see if I can find a specimen.
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Darby




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PostPosted: Jun 25, 2011 10:35    Post subject: Re: I am looking for decayed pyrite and marcasite specimens for research  

Hi Trudy,
I don't know much about minerals myself but i seen pyrite before. i find this strange you mention fossil fuels as i work in oilfield. Last year on a job i found a shell that started converting to pyrite and i have posted picture here on the forums here's the link.
https://www.mineral-forum.com/message-board/viewtopic.php?t=1140
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PostPosted: Jul 27, 2011 20:21    Post subject: Re: I am looking for decayed pyrite and marcasite specimens for research  

Trudy, let me know if you choose to carry this over into pyrrhotite...it also decays into a variety of iron sulfates and its stability seems habit dependent in many locations.

You mention the mining literature regarding pyrite decay. Actually this literature should be quite extensive as many lead-zinc-silver sulfide deposits contain large amounts of pyrite and have some interesting and dramatic decay phenomena like spontaneous combustion. (These deposits should perhaps more accurately viewed as iron sulfide deposits with economic concentrations of other metal sulfides, since Fe represents >60% of the metal budget in most of these systems). In some of these systems...Gilman Colorado for example, stopes had to be backfilled within weeks to keep them from igniting...all realted to very rapid oxidation of pyrite. Other mines were slower to catch on and had mine fires that burned underground for years...like Jerome. I am sure that googling spontaneous combustion, pyrite and suldife ores will give you some very interesting leads.

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PostPosted: Jul 28, 2011 05:51    Post subject: Re: I am looking for decayed pyrite and marcasite specimens for research  

I followed the link Darby provided to the photo he mentioned and noticed there was some interest from the group. I have attached a photograph of a piece of pyrite I found yesterday in a group of drill cuttings. Though the gas reservoirs here (Lipscomb county Texas, USA) are generally sands, the wells have to drill through several thousand feet of non-reservoir sand and black shale to get to the sands. Small clusters of pyrite are common in both the shales and sometimes in the non-reservoir overlying sands. The pyites are most often not oxidized as this sample shows, but sometimes they are discolored.

Can anyone provide information on the origin of the 2 sets of striations?



6850 x35 1mm 2 M1.jpg
 Description:
pyrite
subsurface - Lipscomb county Texas
1mm x 1mm x 1mm
 Viewed:  42217 Time(s)

6850 x35 1mm 2 M1.jpg


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PostPosted: Jul 28, 2011 23:42    Post subject: Re: I am looking for decayed pyrite and marcasite specimens for research  

Darryl...this looks like pyrite overgrowing marcasite replaced by pyrite. There is some very good work dome by James Murowchic (now at Washington University in St. Louis) on this published in Economic Geology back in the 1990s. Google Murocchick and pyrite or marcasite and you'll find it immediately. Your bosses will be impressed...
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PostPosted: Jul 29, 2011 00:16    Post subject: Re: I am looking for decayed pyrite and marcasite specimens for research  

Peter, Thanks for the information. The sequece was certainly more complex than I imagined. I had long suspected that much of the "pyrite" I was seeing in drill cuttings was really marcasite and in fact had even labeled some as such but I never knew for sure. Now the question is: "Does knowing this tell us anything about the origin of the sulfides or the conditions under which each was deposited and/or replaced?".

Although included in the mud log for this well, I had not yet annotated the photo. Now I will have something to put on it and perhaps my client and their partners "will be impressed".
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PostPosted: Jul 29, 2011 09:12    Post subject: Re: I am looking for decayed pyrite and marcasite specimens for research  

Darryl...there's lots of literature about what marcasite versus pyrite can tell you about the conditions of formation. Marcasite tends to be a lower temperature species than pyrite, and forms under more acidic conditions than pyrite. Because of this it is the more common species to encounter in sedimentary rocks, especially organic-rich units. Marcasite is also much less stable than pyrite and if conditions are right it will gradually reorganize itself into pyrite...no replacement is required since the two species have the same chemical composition...but often the original marcasite habit is preserved.

Even if you're stuck in a logging truck somewhere you can google up some papers on the subject

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PostPosted: Jul 29, 2011 09:36    Post subject: Re: I am looking for decayed pyrite and marcasite specimens for research  

Peter, Thank you for the information. I hadn't really thought about it being a re-orginazation rather than replacement but of course you are right.

Being stuck in a logging trailer beats being stuck in the offices or classrooms I used to occupy. Given the time I have to check on things on my own andnearly unlimited access to the internet I find it quiet enjoyable. Just about the best combination of lab and field I can imagine.
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