FMF - Friends of Minerals Forum, discussion and message board

[Erik Buck]

My wife has some jewelry made of cinnabar, HgS, which is a pretty red. It seems to be turning black, possibly changing to metacinnabar? How can she clean it or restore it?

[Peter Megaw]

Is this myrickite...fine-grained cinnabar in fine-grained opaline silica or coarsely crystalline cinnabar? IIn either case the first thing you have to do is start storing it in the dark...ALWAYS unless you have it out to wear...cinnabar is very light sensitive. In addition it is very soft so the most you should use would be a soft cloth and attempt to gently rub off the surface oxidation layer. If the oxidation is incipient you might have a chance to restore some color...if not you are probably stuck with permanent darkening. If it's myrickite you might be able to have it repolished to get down to unoxidized cinnabar.

The same advice about storing in the dark applies to specimens...perhaps more so since you can;t buff them up. Also be wary of heat...cinnabar volatilizes at very low temperature and you could inadvertently liberate mercury vapors, which are not good to be around. On the other hand you won't have to worry about bugs eating the packaging

[Tracy]

A toxicologist's two cents: the likelihood of being exposed to significant and potentially hazardous concentrations of mercury vaoprs is extremely low, when speaking of volatilized mineral specimens or, by extension, jewelry. ("the dose makes the poison"). :-)

- Tracy

[David Von Bargen]

You have to know what you are dealing with. The term cinnabar also applies to a red lacquer which may or may not actually contain cinnabar.

See prof Dietrich's explanation on his website under cinnabar:
https://www.cst.cmich.edu/users/dietr1rv/
(link normalized by FMF)

[John S. White]

I agree with David, but as far as I know the red lacquer does not oxidize and turn black. It is highly unlikely that the beads are solid cinnabar so they may be myrickite, but I have never heard of myrickite turning black either.

[Peter Megaw]

I have a polished piece of myrickite that has darkened significantly...not yet black...on one side. Modern "cinnabar" lacquer contains no cinnabar mineral so it should not darken...old material does however