Artifical Solid Gold Crystal

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lazersteve

lazersteve

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All,

Tonight I was dissolving some gold and wanted to be sure all the nitric from the AR was used up, so I tossed in an 18.3 gram button I had laying around to finish off the excess nitric. When I pulled the button out it had taken on a very beautiful crystaline structure. The following photos do not do the crystal lattice justice. It real life the facets all have hair like striations in them which scatter the light in all directions. The color of the button is a brilliant golden yellow (the photo of the bottom looks closer to the actual color of the nugget).

Here's the top of the button now:

[img:356:356]http://www.goldrecovery.us/images/nugget_natural_top2.jpg[/img]


and the bottom of the crystaline gold nugget:

[img:489:444]http://www.goldrecovery.us/images/nugget_natural_bottom.jpg[/img]

The button weighs 10 grams now and is the most beautiful crystal structure I've ever seen. I'm going to mount a nice stone in the middle pipe and make a necklace out of it.

I'm working on a good photo that captures the color and the lattice. I'll post it when I get the lighting right.

Steve
 
Steve,
I know what you're talking about. I did the same about a year ago and I was very surprised by the unusual shape the gold nugget took. :p

It seems that our hobby still reserves us many surprises :roll:
 
That's very common, Steve. I experienced that on an ongoing basis, although each button has its own characteristics. I used added gold routinely to consume excess nitric instead of evaporating. Saves a lot of time, and insures that the nitric is eliminated. Very nice to see you've picked up the trick. :wink:

Etching is commonly used to define crystal structure in metals. I expect Lou could fill us in on the procedure.

Harold
 
Oh, I can fill you in on procedure all right :). I've etched... a lot of things.

It is pretty, isn't it Steve? You can do the same with a variety of metals, but some do it better than others.

I've etched, Hf, Zr, Nb, Ta, Pt, Rh, Pd, Pb, Cu, Si, and many others.

Some metals need really aggressive conditions (conc. perchloric acid and HF for instance, others want aqua regia, etc.).

As Harold mentioned, this etching gives you the crystal boundaries. What you get depends on how your metal cooled, in most cases, the slower you cool, the bigger the crystals you will get. What you did Steve, was you removed the microcrystalline surface and got to the larger crystal structure underneath. It is larger because it cooled slower and it is also purer inside than it is out (generally impurities tend to aggregate toward the surface if it cools evenly, this is exploited in zone refining) on the surface.

Platinum will do this too in exceptional circumstances.

Lou
 
I was wondering if you could construct (like melting together several formed pieces into a desired shape) a nugget with a specific shape, then etch it to reveal the crystals in side? These would make great jewelry pieces.

I'm going to tinker with the idea a bit.

Steve
 
Something you might try is to pour an ounce or so over rock salt. Dissolve the salt, then etch the resulting "nugget". Could prove very interesting.

I never tried etching one, but I made a few of those nuggets for a friend. They're actually quite pretty, especially when made from ultra pure gold, so there's no oxidation on the surface.

Harold
 
I have some 6N5 (120g) gold and a lesser quantity of the same quality Pt. I'd be willing to offer this material at an attractive price for those interested in growing crystals.


Actually Harold, while they would look pretty doing that with rock salt, I doubt that they would form large crystals. If I were to really take the time and effort to do this, I would either make my crystals by decomposition of AuCl3 or I would put that very, very pure gold of my own into a special crucible and heat it in a vacuum and then let it cool slowly over a period of days. Sometimes really pure material has trouble crystallising and needs to be seeded. Interesting things happen with that.


Lou
 
Lou said:
Actually Harold, while they would look pretty doing that with rock salt, I doubt that they would form large crystals.
Click to expand...
Good point! They cool quite rapidly, so the crystal structure would likely be very fine. In a sense, that's good, for the "nugget" that forms tends to have rather small appendages, with a common core that is somewhat larger. All depends on how the salt comes together, but it stands to reason that the rapid cooling of the appendages would result in small crystals. Could still prove to be more attractive than the 'as cast' surface, but hardly as noticeable as those that Steve displayed for us.

Sometimes really pure material has trouble crystallising and needs to be seeded. Interesting things happen with that.
Click to expand...
Apparently exceedingly high purity has strange effects on many of the elements. Some time ago I recall reading in the Smithsonian magazine that a Japanese company was researching ultra high purity iron, (6N's and better), which they claim became corrosion resistant.

Harold
 
Alot of people on ebay have bought home made nuggets that looked like natural ones.

I never sold any this way though.

Just saying.

Mark
 
He's [Harold] right about the iron. I don't have the source either, but I know from personal experience that UHP iron is more difficult to dissolve.

As he said, the purer you get, the more things start behaving strangely.
 
Scott2357 said:
Harold,

Do you remember the source about ultra pure iron? Link?
Click to expand...
No link----but if you have access to any of the Smithsonian magazines, say back a year ago or more, it was just an advertisement that ran on one of the pages. It appeared regularly for a while----don't recall seeing it lately, although I haven't spent as much time with the magazine due to my hectic schedule.

Should you go looking, I recall the ad was just in black and white, and not large. It would be easy to overlook. If I happen to run across the ad, I'll post notice here, perhaps even a scan. Very little was mentioned, just the fact that pure iron behaved as if it was inert.

Harold
 
The reason I asked was I have an object that I was told behaves as you described. It's what I believe is a metorite. I've seen several metorites before and found a couple myself, but this one is different. It was about 3x1.5x1.5 inches and very hard with no signs of melting on the surface. It was charred black on the outside but the inside looked similiar to pyrite but a little darker. I found it when I was about 14 and I remember my dad had to give it several full swing hits with an 8 lb. sledge hammer on concrete to even chip it. He worked at a big chemical company at the time(Monsanto) and knew some guys in their lab so he took the chip in to be tested. They told him it was the purest form of iron they had ever seen and it appeared not to oxidize at all. Normal test acids had no effect. Only a mixture of acids used to dissolve PMs ( I would assume AR but don't know for sure since they never told us the names) had any effect and then only left a bronze colored stain on the surface. I thought they were probably just yanking my chain but it sounds like it might be true. I have it in box somewhere in the garage now but haven't seen it since we moved.
 
Interesting. If you happen to run across the thing, it might be nice for readers to see a picture.

I don't imagine many of us have ever seen, let alone found a meteorite.

Harold
 
Well, I plan to clean out the garage in the next few weeks when I finish up a couple of sets of wedding photos I have to process. When/if I find it I'll be sure to post a pic. Then I can relate the story of how I came to possess it.
 
Some meteorites have been proven to be older than earth itself.

Talk about antique!

Gotta love' em. :D

Mark
 

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