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Techniques for CollectorsCleaning pyrite / marcasite samples found in black shale...
23rd Nov 2015 17:11 UTCScott DeLano
Quick question...I have found several nice little pyrite and marcasite samples within black shale deposits in northeastern Oklahoma. After picking at them with a dental pick, I wasn't very happy with the results and the time it takes. So I had someone that I know, who etches glass with a blaster take a shot at a couple of the samples. They use Black Silicon Carbide (180 grit) material to blast with. It took the black shale right off and left the crystals but now those three samples are dull gray color. I thought I would just need to do my usual 6% vinegar and then soapy wash to get them to shine and clean off the gray. Instead, the samples are staying that dull deep gray color. Is that normal or did the blasting material somehow recolor my samples (I can't believe that would happen)? If it recolored my samples, what blasting material would be better to use in the future? Thank you!
23rd Nov 2015 17:16 UTCAlfredo Petrov Manager
23rd Nov 2015 17:36 UTCRob Woodside 🌟 Manager
23rd Nov 2015 18:43 UTCMichael Sommers
23rd Nov 2015 19:39 UTCBob Harman
Several years ago I found a large number of silvery finely striated pyrite cubes up to 2cm in a nearby quarry. They had never been reported there before. Anyway they all cleaned up quite nicely as they were in a carbonate rich matrix. Several of the nicest are now at the museum with a new locality report. With a bit of luck, maybe yours will come out as nice as mine did! CHEERS.......BOB
23rd Nov 2015 19:48 UTCScott DeLano
23rd Nov 2015 19:50 UTCDonald Lapham 🌟
23rd Nov 2015 22:15 UTCScott DeLano
24th Nov 2015 21:53 UTCJohn Oostenryk
But actually, yes, do consider the frictional 'heat' generated by striking and abrading. In the micro view picture- similar to a grinder being used!
I have used baking soda as air abrasive on pyrite and found even that can leave a matte luster on the surface of some. It is worse on marcasite and especially on
prior chemical altered surfaces( like when colored red or yellow by prior alteration.)
It is certainly something you have to experiment with on lesser pieces before utilizing on your best.
SAME thing with chemical prep- test crap stuff first!
Are you wanting the pyrite free of the matrix or just to clean up the pyrite? Just thought I would ask that for clarity.
I find that many shales tend to disintegrate when wetted after being dug up. This can vary from repeated rains to literally just dipping in water for 2 seconds.
Be careful about your matrix being immersed in a chem bath, test first...
~JO:)
30th Nov 2015 21:04 UTCScott DeLano
30th Nov 2015 21:34 UTCBob Harman
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Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2024, except where stated. Most political location boundaries are © OpenStreetMap contributors. Mindat.org relies on the contributions of thousands of members and supporters. Founded in 2000 by Jolyon Ralph.
Privacy Policy - Terms & Conditions - Contact Us / DMCA issues - Report a bug/vulnerability Current server date and time: March 29, 2024 08:42:39