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Light sensitivity of cinnabar crystals (Chatian Mine, China)?
  
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Tobi




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PostPosted: Jan 29, 2017 14:10    Post subject: Light sensitivity of cinnabar crystals (Chatian Mine, China)?  

Hi,

while presenting this new cinnabar specimen below, I was reminded of the light sensitivity of this mineral:
Carles Millan wrote:
Carles Millan wrote:
Keep the deep red cinnabar crystals covered before they get dark. Unfortunately I failed to do so many years ago :-(
Tobi wrote:
I know about that problem :-( Do ALL of them get dark or is there a chance that this may not happen to certain specimens? Tobi

I think all of them are light sensitive, but there are plenty of knowledgeable people in the forum that can answer such question much better than me. Good luck!

I hope Carles is right and some of you are more knowledgeable about cinnabar. So my question is: Are ALL cinnabar specimens (especially from Chatian Mine, Hunan, China) light sensitive and get dark when exposed to sunlight or is there a chance that this specimen is not affected and will keep its colour even though presented on display?

Thanks
Tobi



CinnCHAT.JPG
 Mineral: Cinnabar, Quartz
 Locality:
Chatian Mine, Chatian District, Fenghuang, Xiangxi Autonomous Prefecture, Hunan Province, China
 Dimensions: Specimen height 5,5 cm, largest cinnabar crystal 8 mm
 Description:
 Viewed:  2130 Time(s)

CinnCHAT.JPG


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lluis




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PostPosted: Jan 29, 2017 16:28    Post subject: Re: Light sensitivity of cinnabar crystals (Chatian Mine, China)?  

Tobi, as far as I know, and chemistry says, all cinnabars are light sensitive.
Colour could be restored by heating the specimen until it sublimates... Crystals formed would be again red... (and the perfomer would probably get mercury poisoned, and specimen for sure destroyed).

I keep my specimes in a dark place, and they resist far time better than I...
So, just keep them far from sunlight (or any light, maybe except the low energy ones....)

With best wishes

Lluís
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Jordi Fabre
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PostPosted: Jan 29, 2017 22:44    Post subject: Re: Light sensitivity of cinnabar crystals (Chatian Mine, China)?  

Tobi wrote:
...I think all of them are light sensitive...

Yes Tobi, for sure them all.
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MIM Museum




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PostPosted: Jan 30, 2017 02:38    Post subject: Re: Light sensitivity of cinnabar crystals (Chatian Mine, China)?  

Gentlemen

I am not sure the cinnabars are sensitive to light (provided the latter does not contain UV). The color of cinnabar is not due to impurities or defaults, but to the chemistry of mercury sulfide itself.

Look at this 4.8 cm cinnabar twin from China whichhas been displayed as on the picture since October 2013 (with LED backlighting). Its color has not budged :

http://3.bp.blogspot.com/-ISPXqgy2Zns/Ul7m233M1CI/AAAAAAAATdg/g2doOZESfMQ/s1600/DSC01687.JPG

Salim

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Tobi




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PostPosted: Jan 30, 2017 11:14    Post subject: Re: Light sensitivity of cinnabar crystals (Chatian Mine, China)?  

Thanks guys, so the bottom line is: Yes, all cinnabars are light sensitive but no, not all of them fade quickly ;-)
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Carles Millan
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PostPosted: Jan 30, 2017 11:38    Post subject: Re: Light sensitivity of cinnabar crystals (Chatian Mine, China)?  

Tobi wrote:
Thanks guys, so the bottom line is: Yes, all cinnabars are light sensitive but no, not all of them fade quickly ;-)

I hope yours will be low speed.
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Matt_Zukowski
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PostPosted: Jan 30, 2017 12:56    Post subject: Re: Light sensitivity of cinnabar crystals (Chatian Mine, China)?  

If I understood what you typed Tobi, I don't think it is correct to say that "not all of them fade quickly." Salim's cinnabars have not faded, but that is because they are under LED lighting which has a narrow spectrum and lacks UV or whatever other wavelengths that fade cinnabar. The speed of fading may well vary from locality to locality, but if you put cinnabar in daylight and maybe other types of light, they will fade, probably all too quickly.
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Tobi




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PostPosted: Jan 30, 2017 16:22    Post subject: Re: Light sensitivity of cinnabar crystals (Chatian Mine, China)?  

You're right, Matt, I guess keeping it in a box and hidden from sunlight is the best - or the only - way to keep its red colour ...

Thanks
Tobi
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Jordi Fabre
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PostPosted: Feb 01, 2017 00:24    Post subject: Re: Light sensitivity of cinnabar crystals (Chatian Mine, China)?  

Tobi wrote:
...So my question is: Are ALL cinnabar specimens (especially from Chatian Mine, Hunan, China) light sensitive and get dark when exposed to sunlight...

This was the header of this thread. As Salim well said them seems not be sensitive to the LED light but I assumed on my previous answer:
Jordi Fabre wrote:
Tobi wrote:
...I think all of them are light sensitive...
Yes Tobi, for sure them all.
that we were talking about the sun light.

Jordi
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alfredo
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PostPosted: Feb 01, 2017 11:13    Post subject: Re: Light sensitivity of cinnabar crystals (Chatian Mine, China)?  

It would be interesting to experiment and find out exactly which wavelengths (colours) of light cause destruction of cinnabar. Most people assume that UV is the culprit, but it might be green light, as it is in another light-sensitive red mineral, realgar. LED lights (my primitive ones anyway) are rather poor in green light, which might be why cinnabar survives LED light longer than other lights?

In order for light to destroy a chemical bond, the energy of that light has to be absorbed by the mineral, not transmitted or reflected, and realgar absorbs green light very well. If you have any low-quality or broken cinnabar crystals, you could experiment with filters of different colors. Experimentation beats speculation every time ;))
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Tobi




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PostPosted: Feb 01, 2017 11:30    Post subject: Re: Light sensitivity of cinnabar crystals (Chatian Mine, China)?  

Yes, my question was relating to natural sunlight.

alfredo wrote:
[...]If you have any low-quality or broken cinnabar crystals, you could experiment with filters of different colors. Experimentation beats speculation every time ;))
Great idea! So where are our volunteers to sacrifice their cinnabar crystals?!
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lluis




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PostPosted: Feb 02, 2017 05:22    Post subject: Re: Light sensitivity of cinnabar crystals (Chatian Mine, China)?  

Hi, Alfredo, Tobi, List

I think to have read here that green light is what causes fading of color of cinnabar. And for sure, cinnabar absorbs green light (for that it looks red...)
Anyway, as to the question that Tobi asks, I am not a volunteer to sacrifice one of my pieces....
Maybe if I find a small one, but I think that I have gifted all the ones that were not in collection....

With best wishes

Lluís
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Tom Tucker




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PostPosted: Feb 02, 2017 10:21    Post subject: Re: Light sensitivity of cinnabar crystals (Chatian Mine, China)?  

I have collected red cinnabar rhombohedral crystals from an open, south facing-exposed surface near Terlingua, Texas that must have been exposed to the southern Sun for decades, and they remain red, even to this day. That was over 40 years ago, and they're still red.
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Tobi




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PostPosted: Feb 02, 2017 10:29    Post subject: Re: Light sensitivity of cinnabar crystals (Chatian Mine, China)?  

Tom Tucker wrote:
I have collected red cinnabar rhombohedral crystals from an open, south facing-exposed surface near Terlingua, Texas that must have been exposed to the southern Sun for decades, and they remain red, even to this day. That was over 40 years ago, and they're still red.
Nice to know! :-)
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Jordi Fabre
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PostPosted: Feb 02, 2017 11:34    Post subject: Re: Light sensitivity of cinnabar crystals (Chatian Mine, China)?  

Tom Tucker wrote:
I have collected red cinnabar rhombohedral crystals from an open, south facing-exposed surface near Terlingua, Texas that must have been exposed to the southern Sun for decades, and they remain red, even to this day. That was over 40 years ago, and they're still red.

They could be Comancheite or Montroydite?
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PostPosted: Feb 02, 2017 11:48    Post subject: Re: Light sensitivity of cinnabar crystals (Chatian Mine, China)?  

Peter Lemkin wrote:
While I'm sure there are other and newer articles on this, one online here
http://www.minsocam.org/msa/collectors_corner/arc/cinnabar.htm
(link normalized by FMF)
in the American Mineralogist from 1938 seems to indicate some types are much more sensitive than others depending on minor chemical variations.

To know more about how to publish links in FMF please read: Links within the message forum
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PostPosted: Feb 02, 2017 16:47    Post subject: Re: Light sensitivity of cinnabar crystals (Chatian Mine, China)?  

Jordi, hope you're enjoying Tucson. I'm certain the little Terlingua crystals are cinnabar. Comanchieite would be tetragonal, and these are definite rhombohedrons, like little red calcite crystals would be. I don't want to hijack this thread, so let me open a new one concerning some Terlingua montroydite. Tom
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