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Mercury staining is another bit of folk lore in the jade collecting world.
So called mercury staining on a piece of jade is not mercury unless you are looking at the bright red stuff known as cinnabar, which is mercury sulphide.
Dealers in the markets love to use this term to offer credibility to a piece, as we all know the ancients scattered mercury or its salts all over the grave.So mercury staining is a good sign of indirect provenance, isn't it? Mmmmmmmm!
Most of the dark brown, purpley brown colouring blamed on mercury is actually iron staining, or alteration of the iron in the nephrite (actinolite/tremolite).May be if mercury was ever in the vicinity of the buried object, it is such a biocide, that it stopped the normal oxidative process of decay and changed it to an anaerobic environment.This may have affected the type of iron salts present, giving the darker colouring.
Cinnabar is red, if it is cinnabar and not poster paint or similar.Cinnabar is relatively inert so will not dissolve in water, or acetone like poster paint or acrylic paint.(A good reason to wash your jade pieces, you get to see all the details the faker was trying to disguise with dirt!)
Cinnabar will only change to the darker purple brown coloured metacinnabar at 345 degrees celsius.So if any one disputes the colour of your jade piece, and says it is not iron but metacinnabar, ask them to hold it. If it is metacinnabar, they should burn their hand.
So claims about mercury staining and it is not bright red, then the likely hood is that it is only iron staining of one form or another.
Mercury staining can be confined to the same cupboard as,"It is the only piece found like this" and "Its been in the family generations" or similar.
Happy hunting
Mike

First of all, we need to separate cinnabar and mercury. Cinnabar(HgS) is no doubt in red powder form. But, mercury(Hg), the so-called "Quick Silver" is in liquid form. That was used extensively during certain dynasties. The most famous was that Qin Qi Huang Di(The First Emperor)'s burial had used the largest volume of liquid mercury to signify rivers. The toxic fume released from mercury kills the pest, bateria, and the wourld-be tomb-raiders. The signs of excessive amount of mercury in the burials have now been detected around the site in Xia

I disagree!

Tree sap and iron-oxide can produce dark brown to the so-called Lao Tu Da Hong. Cinnabar can produce the so-called rosey-red permeation.

The amount of mercury used, and the concentration of mercury in the burial can definitely stain nephrite to black color. If what you said is true, then all the Hai Qi Gu black color permeations are fake! This is obviously a mistake!

But is it actually the mercury causing the colour to go black? Is it not the strong reduction of iron salts/ions to give a dark colour.It is not a black mercury salt.Possibly the mercury is indirectly causing the reduction of iron to go black, as I previously stated.
Has someone actually detected/measured that the cause of Hai Qi Gu is due to mercury?
Note I am not saying these pieces are necessarily fakes, but the attribution to mercury alone is questionable.I would expect some other element such as Fe to be responsible.
Regards

Mike

I 'll talk about the different Keng-types of burials that the traditional jade collectors attribute under a new thread.

We need to know the difference between Da Keng(large burial) and Xiao Keng(small burial). Da Keng were for the imperial family and high-ranking officials especially those who were given land and titles of King, Duke, Marquise, Count, Viscount, Barron, etc. Xiao Keng were for wealthy tycoons. Poor people might not even have jade in their burials.

The ancient people used a much larger volume of liquid mercury in a Da Keng. They used smaller amount of mercury in a Xiao Keng. The liquid mercury sank to the bottom of the burials, thus staining the jades. The degree of black mercury permeation indicates the kind of burial and the age of the jades. Most Hei Qi Gu should weigh heavier than the jades that have no permeation because mercury is a dense mineral that increases the weight of the jades after the permeation.

Hei Qi Gu or jades with heavy mercury permeation(those that were not fully-absorbed with mercury but show windows of the original material were mostly from Da Keng. For the jades that only show sporadic tiny spots of dark mercury permeation or no mercury permeation, they were mostly from Xiao Keng.

The intensity of the mercury permeation indicates the age of the jade. Mercury were widely used since Xia, Shang and Zhou. The Tang Hei Qi Gu usually appear less intense than the Han or Warring States Hei Qi Gu because the longer the permeation, the more intense the color. Song and Yuan Hei Qi Gu appear even lighter in color.

Understand these things can help identify and determine the age of jade. Artificial black dye would fade and left behind the dye that trapped in the veins of fissures of the jades. Real Hei Qi Gu has a crisp hand feel just like other Sheng Keng when dry. Artificial dye or painted black color on the jade surface do not feel the same. Anyway, an old jade and a jade with new work do not feel the same in the hand!

What is the mercury combining with to form this dark stain? It has to react with something.Is the knowledge of mercury staining derived from classical texts?
With all that mercury about, it would have been in danger of destroying, by creating an amalgam, any precious metals that were put in the tomb, if it came in contact with them.
I remain to be convinced that mercury directly causes the black staining.What is the chemistry of the reaction involved?

Cheers

Mike

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