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Silver Mercury alloys

Posted by Reiner Mielke  
Reiner Mielke July 12, 2011 12:25AM
Can minerals such as Eugenite and Luanheite be created just by adding Mercury to regular silver?
David Von Bargen July 12, 2011 02:12PM

I believe there was some luck making them electrochemically.
Jim Daly July 12, 2011 05:27PM
Adding mercury to silver results in an amalgam- a solid solution without crystallinity. This is what dentists used to use to fill tooth cavities. Eugenite and luanheite have a crystalline structure.
Reiner Mielke July 12, 2011 05:34PM
Hello Jim,

If you added mercury to silver which has a crystalline structure ( such as a silver leaf or crystal) surely the mercury would not destroy that but rather just bond to the existing structure?
Evan Johnson (2) July 12, 2011 05:46PM
The way I see it, the mercury would either have to adsorb onto the surface, or dissolve into the crystal. Mercury is a pretty big atom (so big, in fact, that it has aurophilic chemical behaviour- to what extent that plays a role in this story I have no idea, with self-affinity versus affinity toward silver). But it would seem strange to me if the lattice of a native metal was preserved upon adding liquid mercury(at least beyond a threshold).
Rob Woodside August 29, 2011 10:51PM
Mineralogy seems to have a hard time with alloys. They have the structure of the major component and are regarded as mixtures and mere varieties of the dominant component and not fit for a mineral name. This is the fate of amalgam and electrum. The growing number of amalgams christened with mineral names are intermetallic compounds with a definite composition and unique structure. It is perhaps surprising that Ag and Hg produce such a large number of intermettallic compounds.
Reiner Mielke August 29, 2011 11:41PM
Isn't dentist's amalgam just a mixture of mercury and powdered silver? Does it form crystalline structure once it is in your tooth? and if so what mineral would it be? Would it be possible to artificially create the different amalgam minerals in this way by varying the amount of mercury?
Rob Woodside August 29, 2011 11:58PM
Amalgams still have the face centred cubic structure of Ag. It could be that the Hg is cementing the Ag grains with little diffusion of Hg into Ag in dental "amalgams". Given time or heat the Hg would probably dissolve in the Ag and if in right proportions might even make an intermetallic compound.
Alfredo Petrov August 30, 2011 12:50AM
Dental amalgams are not exact analogues of any natural mineral silver amalgams, because modern dental amalgams contain tin, copper and sometimes other metals in addition to the mercury and silver.
Rob Woodside August 30, 2011 01:47AM
Ah yes Bart Cannon probed Jack Zekster's filling and got what Alfredo claims.
Riccardo Modanesi August 30, 2011 10:18AM
We could create a whole systematic nomenclature of alloys, according with metals they are compounded by and the percentage of compounding metals! For example, how many gold-silver alloys should we have? Undefinitely many! Let's think of how many metals are suitable to create an alloy!
Greetings from Italy by Riccardo.
Rob Woodside August 30, 2011 09:33PM
Hi Riccardo, It was good to meet you at the Mindat conference.

The natural gold silver alloys break into three groups: nearly pure Au, around 80% Au, and around 60% Au (electrum). Sadly geology has little to do with mineral nomenclature so these alloys are just called Gold.
Nelse Miller July 05, 2012 08:22PM
Seeing this topic takes me back about 50 years, to a somewhat simpler time. In high school, I had a book called "Crystals and Crystal Growing" in which the following experiment was described. Take a 5% solution of silver nitrate and put it in a convenient sized test tube. Add a drop of mercury metal and let everything stand overnight. The next morning, you will find a cluster of thin silver amalgam crystals on the bottom of the test tube. I tried it and it works. As to what the composition of the amalgam was, I can't say. As an aside, can you imagine anyone these days giving a high school student silver nitrate and mercury? Or rather, giving it to anyone not employed in an "official" laboratory?
Travis Olds July 05, 2012 08:52PM
Here's a link to an article describing the experiment above. There's even a picture of the crystals they grew! I do not remember if they assign the phases they studied a specific mineral name; just called them beta and gamma amalgam.

Or if the link doesn't work, Google the "Effect of heat on the structure of single crystals of silver amalgam." Should be the first hit. Then scroll down to May 1965 to find it.

Edit. They studied three phases, alpha, beta, and gamma. They suggest a formula of Ag3Hg4 for the gamma phase.

Edited 1 time(s). Last edit at 07/05/2012 09:01PM by Travis Olds.
Bart Cannon July 05, 2012 11:52PM
Rob is correct about the fact that I analyzed a filling that fell out of Jack Zektzer's mouth.

My interest in dental amalgams began twenty five years ago as a result of using a pocket "TENS" unit designed by Steve Satra.

I can't remember what "TENS" means, but it produces a small shock that stimulates endorphin production. They can be used on any part of the body that is producing pain, but I clipped the electrodes on each ear lobe to relieve the frequent headaches I ounce suffered from. I haven't had a headache since about the time bought the TENS unit.

Anyway, when I cranked up the amplitude on the unit, I noticed that I could easily detect a metallic taste in my mouth, and surmised that metals were heading away from my my fillings.

Dental amalgam contains silver, mercury copper, and TIN.

At about the same time Jack lost a filling and I made a polished section of it and a video BSE movie of the analysis and showed it at a little mineral bourse South of Vancouver. That is how Rob knows about this since he was present and viewed the movie.

The interesting finding was that the filling showed voids which contained beautiful crystals of a tin chloride, suggesting dissolution and re-distribution of metal.

I am not a health alarmist and I would not dream of having my fantastic mercury amalgam fillings removed and replaced. The main reason being that copper in dental amalgams is a bacteriacide which slows the deterioration along the margins of the fillings. The modern epoxy fillings don't have that benefit and they are more expensive.

Plus the exposure to mercury during a filling removal would require a HazMat team if the regulations were followed. Luckily they aren't

I remember being told 40 years ago that my fillings would need to be replaced within 10 years. I still have all my fillings and all of my teeth.

Reiner Mielke July 06, 2012 12:16AM
Trouble with amalgam fillings is that they do not stengthen your tooth just fill a void ( unlike epoxy which actually glues your tooth together). As a result I regularly have pieces of my amalgam filled teeth break off which I then get replaced with epoxy ( four more to go). LOL
Bart Cannon July 06, 2012 12:37AM

This should probably be a private e-mail, but I have a bit to vent about dentists which kind of relates to amalgam.

The strength factor was the theory that was presented to me by my dentist for my last filling a year ago.

But there is still a porous margin between the epoxy and the tooth. I'll report back when that tooth fails.

I went with that advice, but I have quite a few horror stories about dentists. Five years ago my dentist told me I needed to have a molar pulled.

I still have the molar, and have so far been spared the $4,000 to have the replica installed. The original is perfect unlike the simulation would be.

Maybe my amalgam filled teeth are weak, but I've still got all those teeth filled sometime near the end of the Eisenhower administration, as well as those few filled during the Clinton administration

A dentist thinks his job is to grind out a cavity until all you have left is an eggshell of your tooth.

I think teeth and bone are minerals. Bone is hydroxylapatite. I don't know what mineral a tooth is similar to.

Alfredo Petrov July 06, 2012 12:55AM
The mineral portion of a tooth is hydroxy-apatite too, like bone but denser. The whole idea behind fluoride-bearing toothpaste and fluoridated drinking water is to slowly convert that hydroxyapatite into the bacteriologically more resistant fluorapatite. (Remember the hysteria some decades ago about fluoridated drinking water, that "communist plot to destroy America"? :-S Sort of reminds me of some of the right wing hysterics nowadays... :)-D )

Edited 1 time(s). Last edit at 07/06/2012 12:56AM by Alfredo Petrov.
Dr. Paul Bordovsky July 06, 2012 09:14PM just haven't learned the secret handsign to flash to your dentist, cluing him (or her) in that you are an insider
with knowledge of the game.

> A dentist thinks his job is to grind out a cavity
> until all you have left is an eggshell of your
> tooth.
Tim Jokela Jr August 08, 2012 08:01PM
Seinfeld enthusiasts will suggest that this thread is becoming anti-dentite in nature.

Love the story of tin chloride xls in a filling.

Mineralogy is endlessly amusing!
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