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Dahlonega Gold Analysis -X-Ray-
asheland
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Today I took my Dahlonega Gold Dollar to my friend who has an X-ray machine. This obviously was scanned through a PCGS slab, but the results are interesting. Note: there was more on the screen, but I didn’t get a shot of the rest. The largest readings after gold are shown in order:
The obverse was scanned:
23
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I’m a bit surprised the gold content wasn’t closer to 90% even with minor wear factored in. Georgia gold, natively, purer than many other gold sources.
nice
I believe it’s 90%, the mixture is probably just uneven.
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Very cool!! I know that the experts on this forum will comment. Still, as a non-expert, I have read that before 1854, the Dahlonega Mint produced gold coins with more silver content than Philadelphia, which contributed to a slightly different color. Some early coins had 3.7 - 5.0% silver content before 1854. An 1855-P gold dollar has been reported to have about 1.13% silver for comparison. You should take my 1843-D Quarter Eagle with you next time to compare the two!
That looks like a Thermo Scientific HH XRF. Wow, a lot more PGEs than I would have thought (platinum group elements - Os, Ir, Ru, Rh, Pt, Pd). There is probably another % of Os and Ir combined, and probably another % of Re at least as all three of these would be hard to separate from the other PGEs. Then the rest should be Cu and I am surprised it was not identified in the few to maybe 10% range(?). The open question is why are all of these PGEs in the gold? Generally by the 1830s they had methods to separate the 'platina' from the Au during refining (this was possible in the 18th century, well b4). So really there should not be much there (?). I need to look into how they refined gold at Dahlonega and the other mints. If you have other gold coins to zap with the HH-XRF unit it would be interesting to see the values
Best, SH
Cool information. Nice to have a friend with an instrument like that.
It would be interesting to see one from each mint, just to see the differences.
just in case anyone does, is doing or is planning on doing some sort of sample using xrf or like devices, probably best to scan a coin 3-4x in different spots and get an average. fwiw
i had some done over the years but i only did a 1 off scan, so in retro, i would have done more per coin, especially counterfeits and/or between different mints/denoms etc.
I'm surprised there is no copper being shown in the results.
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Cool results, thanks for sharing.
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The screenshot only shows part of the results-- I suspect copper does show up in the results, lower down the list.....
I thought the same thing! I expected 90% gold, 5% silver and 5% copper.
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I figured this thread would produce some interesting discussion. 👍
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Interesting results, still its worth it to hang onto it
Have you established a baseline for the scanner? I would test several different types, including a modern 90% Commem and a .999 Eagle!
Do we know that most or all of these coins were struck in native Georgia gold?
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When the gold rush began in California, many gold miners in Georgia and the Carolinas went west to join the gold rush. It seems reasonable that some of the gold they found was sent back home to be coined. Of course, the San Francisco Mint opened in 1854 which meant the raw gold could be coined locally.
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"Everything you say should be true, but not everything true should be said."----Voltaire
Fun.
I was thinking more in terms of foreign gold coins being converted to US coins. That was certainly done in Philadelphia. I don't know if it was also done at the branch mints.
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Neat results. Have you shot a P,D,S mint pre-33 gold and compare the results?
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There is no question that California gold was deposited at the Dahlonega Branch Mint
1851-1854 or thereabouts would have been the years where the biggest amounts showed up
Regarding foreign gold coins they did circulate in “Gold Rush” California and yes they were deposited at the SFBM for melting.
I believe some foreign gold coins must have been shipped from SF to the New York Assay office where they were melted into bars before being shipped to the P mint for coinage
Spanish and other foreign gold coins circulated widely in the US so I can't imagine there weren't some converted to US gold coins at the Dahlonega and Charlotte Mints although I think a lot more were converted at the New Orleans Mint since it was located in a major port city.
Worry is the interest you pay on a debt you may not owe.
"Paper money eventually returns to its intrinsic value---zero."----Voltaire
"Everything you say should be true, but not everything true should be said."----Voltaire
Clair Birdsall’s 1984 book “The United States Branch Mint at Dahlonega, Georgia: Its History and Coinage” provides a comprehensive study on the composition of Dahlonega and the sources for the raw materials based on the records of the mint and later XRF analysis.
Forum member Carl Lester @GeorgeKellogg wrote an excellent article on the coloration of Dahlonega gold found here: which touches on many of the questions asked. I have Birdsall’s book and will post the tables on sources of the material if people are interested.
https://www.goldrushgallery.com/news/coloration.html
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Great idea!
Since the displayed elements total 94.198, that will leave over 5% in other materials. So Cu should be a prominent percentage. Cheers, RickO
I have examined the SFBM records foreign gold coins were melted and re-coined at the SFBM
It is my understanding that when raw gold was received at a Mint before 1873, it was melted and the slag removed, then assayed, and if the assay was less than 90% pure gold was added to bring it up to 90%, but no attempt was made to remove the trace elements. In other words they did not refine it down to pure gold and then re-alloy it. They just left the natural alloys in.
You have a Bechtler dollar. Run it through and see how it does.
Do you have a slabbed 1/10 oz. AGE we can use for a comparison? It would be interesting to know how much noise is in your reading from the coin being slabbed.
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So each of the metals and the compounds they are bound up in have specific toning and luster characteristics, though gold alone will never tone, only the metals it is alloyed in in a coin. This raises questions about what metallurgical analysis the various mints were doing on metals they were using since they had to have the sum total of gold in the coins that they were producing.
I need to do that next time I’m there.
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I know that some California gold had trace amounts of Iridium in it. The P Mint tried to separate most of it from the CA gold deposits they received. They couldn’t get all of it
Iridium was viewed as being detrimental to rolls, punches, dies etc. used in coinage because of its extreme hardness
I really wish I had thought to bring the Bechtler! I will have to take it down and do an analysis on it, the only problem is, this week I was off all week and had the time to get down there, and now it’s back to work.
I will try to make an effort to get the Bechtler scanned at some point.
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Cool results, thanks for sharing.
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You’re welcome. 👍
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