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"Pyrite Disease"

Posted by Robert Simonoff  
Re: "Pyrite Disease"
August 21, 2009 02:12PM
I was told years ago that soaking pyrite/marcasite pieces in hydroquinone helps fighting the decay. I have no details on dilutions, rinsing, drying, etc. An old trick, which I have not tried myself.
Re: "Pyrite Disease"
August 21, 2009 03:51PM
Pyrites aand Marcasites are subject to chemical weathering upon exposure to oxygen and water. The water can come from just the humidity of the air. Some pyrites are much more stable than others, but all, given time, oxygen, and water will decompose. The sulfide in the molecule become oxydized to sulfate as the oxygen combines with the sulfur.

Just as an aside, this it the basic reaction that occurs in the formation of acid mine drainage.
avatar Re: "Pyrite Disease"
August 21, 2009 05:29PM
Couple of good articles about pyrite disease.

Government recommendations:

Matrix can cause problems as source of water - re: halloysite

Under these conditions, relative humidity is unimportant: water for the reaction comes from a local source, and hydrous iron-aluminum sulfates act as “getters” for more water. Drying the materials worsens the problem by producing a dust that easily spreads to seed pyrite disease in other specimens. These seeds rapidly re-hydrate at higher humidity.
Re: "Pyrite Disease"
August 21, 2009 06:00PM
I can't add to the great comments that have been made here. As a pyrite collector for 30 years, however, I have found that once the pyrite oxidation has started its a self contained reaction and you are best to throw the specimen out, simple but sad.
Re: "Pyrite Disease"
August 21, 2009 08:23PM
I worked at the Sullivan Mine in Kimberley BC in the 70s and early 80s and have seen sulphide oxidation first hand. The mining procedure at the time was pillar mining where they would drill and blast a large volume of rock called a pillar then muck it out. The process left tons of sulphide based ore open to air where it would start oxidizing to the point where the rock would actually melt!. You can imagine the logistical problems this would cause with equipment, manpower etc. The main minerals were galena, sphalerite, pyrrhotite, and many other minor sulphides. Locally this phenomena is well documented and I'm pretty sure one of those old miners would be happy to share a "hot muck" story.

Re: "Pyrite Disease"
September 11, 2009 11:43AM

Please search for topic:

"Thiobacillus ferrooxidans" 2 years ago.There is an extended conversation about the same subject.Killing the bacteria and keeping dry won't help stopping the decomposition.

I'd like only to note here that the compounds required to stop the decomposition are very expensive!One should try only when talking about very important specimens.I have Pyrite from Madan only and I keep them in open air,I even clean the with acids and I wash them with water.They are so stable that even old pieces that had such treatment long before i handle them are still pristine and intact.It depends on many factors but the locality is very important!

All the best!
Re: "Pyrite Disease"
October 24, 2009 12:26PM
I had a problem with my marcasites (I think they are, they are a little paler than Pyrite, these "bomb" shaped ones). I brushed them clean and then put thin transparent nail paint on them when I was about 16. They now are in open air for 20 years in a humid room with orgids and an aquarium as well. They are not to shiny to look fake, but, indeed, it is a cooping strategy with some negative esthastic result.

There is a tiny chance that all instable ones were lost anyway and I painted only the stable ones, it's 20 years ago....
Re: "Pyrite Disease"
March 01, 2011 08:19PM
Hello There,
I found a rock ~ The rock is heavy for it's size ~ weighing 11.5 ounce's.... It measure's three and three quater's inche's long and is Two inche's wide.... The rock appear's to have quartz also a redish brown coating in some area's.... I wanted to see what was inside, so I took a little saw and tried sawing into it.... On the inside it is just full of bright and shiny silvery color of what I suspect is Pyrite.... Also has numerous cubicle's of golden color.... I did a streak test on rough tile and the streak is black on most ~ also golden on other area's ~ what kind of rock do you think it is and should I do anything to protect the pyrite? Doe's the mineral gold ever mix in with pyrite in a rock? It is a very unusual looking rock and very heavy for it's size....
avatar Re: "Pyrite Disease"
March 01, 2011 09:31PM
I have marcasite specimens that are 40 years old that look as fresh as the day I found them. This is because I treated them. Other untreated pieces turned to dust in a few years. Here is how I treat them and I guarantee it will work on the most unstable pyrite or marcasite. First you wash all the oxidation off and soak the piece in water for a few days. Then you dry the specimen and submerge it in a water displacement protectant like WD40 for a day or two. Then you dry it and then submerge it in clean regular motor oil for a few days. After you take it out of the oil you set it in the sun on something absorbent and let the motor oil drain for a few days. The motor oil gets into the cracks and leaves a thin film on the surface that creates a reducing environment, end of problem.

Edited 2 time(s). Last edit at 03/02/2011 01:20AM by Reiner Mielke.
avatar Re: "Pyrite Disease"
March 01, 2011 09:37PM
Wow Reiner, you've solved a problem that mineralogists and palaeontologists have been unable to resolve for over a century.
Re: "Pyrite Disease"
March 01, 2011 10:58PM
Trust a Canadian to figure it out! smileys with beer

"If it can't be grown it's gotta be mined. "
avatar Re: "Pyrite Disease"
March 02, 2011 01:01AM
Not only does the WD-40/oil preserve your pyrite, it also keeps it from squeaking too...... >:D<
avatar Re: "Pyrite Disease"
March 03, 2011 04:07AM
I'm sure the mineralogical world will be elated at the revelation of the cure to those pesky squeaking pyrites! :D
avatar Re: "Pyrite Disease"
March 03, 2011 10:53AM
I'm also delighted that Reiner "guarantees" it. Your pyrite safe or your money back!
Re: "Pyrite Disease"
March 03, 2011 05:05PM
calcium chloride in a small dish is a very good desiccant as well
avatar Re: "Pyrite Disease"
March 03, 2011 09:31PM
If it starts decaying after the treatment I'll buy it off you, is that a good enough guarantee?
Or you can just scoff, not do the treatment and lose your specimen.

Edited 1 time(s). Last edit at 03/03/2011 09:42PM by Reiner Mielke.
avatar Re: "Pyrite Disease"
March 03, 2011 09:52PM
The main factors are environmental. I have a very low rate of pyrite mortality here in my flat, but the humidity is never particularly high, and obviously I am careful what I choose to keep.

But I have some samples that I fear for the future, so I'm going to test them with reiner's idea - I certainly can't see how it can do any harm, so I'm prepared to give it a try!

John Mason
Re: "Pyrite Disease"
March 14, 2011 09:27PM

Something to consider too.

About 12 years ago I collected some amazing micros of reticulated pyrite from a mine in the Dolgellau Gold Belt - some of you may have seen a UKJMM note on them.

Some I hung onto, others went to a museum.

Where I lived at the time, 300m ASL in Wales and with hopeless heating, temperatures rarely went above 10C except for occasional heatwaves in the summer months - and then not far above! Humidity was often high, as one would expect in Wales. That is quite normal.

The museum was air conditioned and warm throughout all year round. The specimens I retained lasted just fine - the ones at the museum were dust within a couple of years. I figured temperature to be a major factor based on these simple empirical observations.

I think some varieties of pyrite will inevitably disintegrate quicker than others, but heat pushes the reaction along, based on these observations. Some others will clearly last a long time - I have Spanish and Peruvian pyrites >20 years in my collection that are the same visually as when purchased. Central Wales - my patch - produces some nice marcasite crystals at some localities, but frankly they are hardly worth collecting, as they "go woolly" withion 12 months and that's the first step to a heap of sulphurous powder that can knacker up even stable choice sulphide pieces from elsewhere!

Cheers - John
Re: "Pyrite Disease"
March 23, 2011 06:33AM

Please search for :

Thiobacilus Ferroxidans

in this forum.

avatar Re: "Pyrite Disease"
August 27, 2011 01:47AM
I know, it's an old topic again and I'll probably get spanked, but decomposing Marcasite/ Pyrite are things I've cursed for years in the Upper Tri-State district of WI, IL, IA. My first serious attempt at stabilizing a piece came when I bought a killer piece from Bill Figi Sr. (before Barlow got there!) but it's penalty came with a 2" section that had 1/4" of sulfur powder on top of a marcasite area. The surrounding crystal areas were mat black sphalerite crystals. I used a wire brush and dental picks to remove all the loose sulfur, which exposed the marcasite. I then used a paint thinner to do some more scouring. Finally, the next week I used Rustoleum black mat paint!

While that technique sounds extreme, it has worked flawlessly for over 15 years on that piece and I doubt many of you would question the procedure if I was to produce before and after pictures.

Expanding off from that technique, and working with its success, I've since stabilized dozens of pieces of both pyrite and marcasite by first cleaning off any sulfur using abrasive measures. Then I put a thin coating of some light oil (WD40, mineral oil, or similar) on and bake it in the oven for at a low setting for 2 hours. Remove from oven and serve (:P). Joking aside, as soon as it is able to be handled (couple of hours later), I then spray the piece with an acrylic finishing spray that I buy at a craft supply supply store. It is used as a top-coat spray over artwork such as chalk and pencil to keep from smudging. I use a mat finish and can not comment on the gloss finish. I wait until it is dry and put a second and third spray coating on, depending upon the porosity of the material. Some pieces I have done as many as 5 coatings on.

This revised technique has worked well for me over the last 3 years and I have not seen any degradation of the pieces nor have I smelled any sulfur odors from them either. They are stored in a high-humidity area right inside my glass showcases for the world to see...not in some special containment area.

This is very similar to the other success story written above where the man used fingernail polish to seal it off. I find that the acrylic finishing spray is undetectable to my eye, and I'm sure it would pass the muster for 99% of the people reading this.

For Albert Mura above: Please PM me and I will be happy to pay for the shipping on all the pyrite that you are throwing away!! :D

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