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 Replies: 28 / Views: 8,739 |
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Pillar of the Community
United States
830 Posts |
So what is the usual purity of panned gold?
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Pillar of the Community
Canada
834 Posts |
Depends on the region of the world you are in gothunder, usually around 14-22k
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Pillar of the Community
United States
830 Posts |
Interesting, so when we see the pay dirt totals on "Gold Rush" its not pure gold?
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Pillar of the Community
United States
4008 Posts |
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If you have ever tried to scratch 22-24K gold on a stone, you know before you even apply the acid that it is good. Higher karat gold is very difficult to scratch onto the test stone. I've heard the expression: "It doesn't bite well."
I guess they mean it won't leave a large mark on the test stone like the lower karat will do. Interesting considering that "pure" gold is softer than lower purity 10k, 14k, and 18k gold. Impurities like silver and copper are added to pure gold to harden it for use in jewelry and coins so that it better stands up to handling and wear.  |
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Pillar of the Community
 United States
1721 Posts |
Ed_B, When I first started dealing in gold, I was confused testing higher karat gold. I could never figure out why the higher karat resisted the scratch test on the stone. I don't know why it works this way but the lower the gold karat the easier it is to leave a mark. I'm not so sure the softness of pure gold has anything to do with what kind of mark it leaves on a test stone. I believe pure gold has a weaker bond and when it is scratched onto a test stone it looks more like bits of flake as though it is crumbling in micro pieces and not smearing like a snail trail. I can take stainless steel and leave a nice streak on a test stone. Stainless leaves a nice thick white mark. The pure gold leaves a gritty, spotty looking mark. You can practically blow the particles off the stone. Wouldn't you say stainless steel is harder than gold? I don't think soft or hard makes a difference when scratching onto a test stone. I believe it has to due with the way the metal is held together with its molecular construction. Maybe we can get a fellow forum brainiac to chime in with their Two Cents. |
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Pillar of the Community
Australia
7096 Posts |
raw gold nearly always contains a mixture of other metals.
When gold bars are poured in the gold room on a gold mine a small sample is drilled from the bar and retained.
The retained sample is a "fingerprint" of the metal content in the bar and is kept as a security measure.
I have seen bars that contain a lot of silver (light coloured ), Copper (Deep red) almost pure (Buttery yellow).
At one mine in particular the silver content in the bars is enough to cover the production costs alone.
I also know of a couple of Copper mines that have a high percentage of gold and silver in the Concentrate that is sent overseas for further processing.
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Bedrock of the Community
13014 Posts |
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I don't think soft or hard makes a difference when scratching onto a test stone. I dont know much about the chemistry of it, but to me it would make sense that harder scratches better. Think about when you break things, hard things come off clean and soft things crumble. It would seem to me when you want to scratch something you would want a hard object that holds its integrity and just wears down as opposed to crumbling into larger pieces Again though without the chemistry background of it I could be way off |
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Pillar of the Community
United States
2541 Posts |
That's awesome. I need to go panning one of these days.
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Pillar of the Community
United States
1721 Posts |
basebal21,
This does make sense, however, lead is very soft and streaks the stone like we did with our shorts when we were little munchkins. Soft and crumbly can be two very different things.
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Pillar of the Community
United Kingdom
4208 Posts |
Chemistry time:
Metallic gold is just a big load of various crystals. Pourd or not - it is actually lots of teensy crystals. Where two crystals meet it is dtill strongly bonded but it has a weak spot. The purer the sample, the larger the crystals get (less impurities to screw them up) and so the less weak spots between crystals for every, say, inch. This makes it harder to get a sample scratched off.
When there is impurities, these form crystal structures too, leaving lots of weak spots where these are. The more weak spots, the easier it is to seperate.
Lead has weaker bonds, I assume, due to its mass and density.
But hey, this is application of a theory in chemistry, It could be some unrelated thing. Things like Propellers have no weak spots - they are one single crystal.
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Pillar of the Community
United States
1721 Posts |
BenByfield, I think you forgot to carry the one  . |
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Pillar of the Community
United States
4008 Posts |
"Lead has weaker bonds, I assume, due to its mass and density."
As atomic mass increases, the electron orbitals reach further our from the nucleus, resulting in weaker bonds than for orbitals that are closer in. High atomic number elements tend to be softer or brittle. Gold and lead are of the softer type. Using a chart of the Mohs Hardness scale shows that lead @ 1.5 is softer than silver or gold, both at 2.5. A assume that these are for pure substances. The metal mix in a pre-1933 US gold coin, for example, is around 92% gold and 7% copper with 1% other metals. This is used in coinage because it is harder and wears better when circulated as money.
The use of a stone as a testing medium must rely on more than mere hardness as its measurement. The metallic crystal structure is a strong possibility. It would be interesting to know more about the physics of these testing stones and how they work.
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Pillar of the Community
Canada
3692 Posts |
@sel: There wouldn't be anything wrong with what you've described as long as it's disclosed to the buyer as man-made/manipulated/not-natural. The same goes with stones, as you may well know.
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Replies: 28 / Views: 8,739 |
First Page
Posted 12/07/2012 11:16 am
