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Techniques for CollectorsRemove malachite from magnetite
8th Jul 2012 19:42 UTCGeorge Creighton
On a recent trip to the hamre cu mine tailings Bygland Norway I found a group of magnetite xls ( largest ~3mm ) covered in a thin layer of malachite,,, the magnetite striations and xl form are clearly visible under the malachite coating.
Question is how to remove the malachite without damage to the magnetite.
All suggestions very welcome.
Regards george
8th Jul 2012 19:58 UTCAlfredo Petrov Manager
8th Jul 2012 20:55 UTCGeorge Creighton
This solution ( Vinegar (acetic acid) was also my first thought after citric acid.
The dilemma is that in norway vinegar is normally sold/retailed in 3 strengths table vinegar 5%, pickling vinegar 7% and a concentrated vinegar 35%.
Which of the 3 above do you recommend.
Glacial vinegar is also available but think that is far to strong.
Regards george
8th Jul 2012 21:38 UTCReiner Mielke Expert
8th Jul 2012 22:05 UTCGeorge Creighton
Deffo magnetite compass reaction.
Already have numerous malachites from this locality but no magnetites,,, need to clean these magnetite xls in order to get a better photo of them to post here.
Regards george
8th Jul 2012 22:55 UTCAlfredo Petrov Manager
George, you're lucky! I wish I could get as many different concentrations of vinegar as you do. All I can get is the weakest version: 5%. But even that's strong enough to dissolve calcite and malachite - just needs patience for several days, and changing to fresh acid whenever the bubbling slows down.
9th Jul 2012 03:18 UTCRock Currier Expert
9th Jul 2012 08:11 UTCGeorge Creighton
Will try with the weakest vinegar to begin with, then if no result will work my way up to dilute HCL.
Will give feedback on progress.
Regards george
9th Jul 2012 12:01 UTCPeter Haas
9th Jul 2012 15:31 UTCSteve Hardinger 🌟 Expert
9th Jul 2012 21:24 UTCGeorge Creighton
The vinegar 7% seems to be working some malachite removed and magnetite xls becoming clearer, only worry is the rust colored parts starting to appear in the feldspar matrix ( possibly limonite or goethite ).
Will try a citric acid removal later.
Thanks to all for input.
Regards george
10th Jul 2012 03:52 UTCJohn Oostenryk
Thought I would mention a possible assist to your project.
Is the magnetite only covered by malachite? That would be more complex, of course.
However, If there are exposed 'surfaces of interest' you wish to avoid etching damage to...
This reminded me of the process for prepping Benitoite etc from surrounding Natrolite by dissolving by dilute acid. I have had very good luck with coating clean, dry areas that I wished to protect from acid with clear fingernail polish(cfp). Acid will creep under edges of cfp after a while, so I would then remove, soak in H2O to neutralize,and let fully dry. Either apply more cfp directly OR flake off lifted cfp area with a tweezers and sharp pin, and reapply more.
To remove cfp, immerse in straight acetone** for ~20 min or so and the cfp is gone. Repeat as necessary.
The acetone vapors are flammable of course, and not good to breathe, and personally, I despise the odor, but have also had good luck with mitigating all 3 neg effects by placing the acetone container in a large ziplock freezer bag Or a sealed bucket. This also helps keep the acetone from attracting h2o vapor also.
**(do not use 'nail polish 'remover', it is weak, more expensive, and has perfumes and other neg additives you don't want on the specimen.)
Post some before and after pics too, please, regardless of procedure. Always interesting to see what folks have found.
Hope this helps!
JO:)
ps: I apologize to whoever first posted that CFP trick, I have lost track of where I read it at. John Veevaert at Trinity Minerals advocates wax, that is different process but same results.
20th Jul 2012 20:32 UTCHoward Heitner
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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: April 23, 2024 21:52:11