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Techniques for CollectorsCleaning cinnabar

1st Jun 2018 05:50 UTCCristian Biagioni Expert

Hi all,

I would like to know if someone has experience about cleaning cinnabar.

I have some specimens stained by iron oxides, with cinnabar on dolomite. I tried on an ugly sample using the Waller solution but cinnabar darkens from red to violet.


Do you have any suggestions how to clean cinnabar avoiding its darkening?


best regards,

Cristian

1st Jun 2018 17:05 UTCTed Hadley

I can't answer your question, but I would like to warn you that any chemical process what has the possibility of dissolving the cinnabar must be avoided. The result would be a soluble mercury compound, which is extremely toxic to all animal life and the environment. Mechanical cleaning (water gun, ultrasonic cleaner) is probably your best bet.

22nd Jul 2018 00:26 UTCKeith Compton 🌟 Manager

Cinnabar is known to darken with exposure to light:


For example see the following reference: http://www.minsocam.org/msa/collectors_corner/arc/cinnabar.htm


I think that all Cinnabars darken - some just take longer than others.


So I don't think it is your cleaning method necessarily producing the darkening (unless you are leaving the specimen in solution in the outdoors for an extended period !)

22nd Jul 2018 14:08 UTCThomas Lühr Expert

The Waller Solution IS the cause of the color change in this case!

Do not apply the Waller Solution (or Iron Out) to minerals that can easy be reduced.

Hg2+=>Hg+=>Hg

Also (for example) it turns malachite and other Cu2+ minerals black due to a corresponding reaction.

Also, anglesite turns black while cerussite stays unchanged, strangely. (S6+ => S2- )???
 
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