Spots on gold bullion

Those guns are super effective at reading the amount of all the metals in that gold coin. Personally, I don't think there's anything at all wrong with that gold coin, but just to be safe, if it was mine, I would have it scanned. They couldn't keep selling XRF spectrometers for thousands of dollars if they didn't work. Years ago, if you mentioned an XRF spectrometer on this forum you rec'd all kinds of flak. Not so much anymore because people are finding out that it's a very effective tool!

 

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I seriously doubt that examining a chunk of debris smaller than most sand grains with a reaction ring the size of a pin head with that thing will add any useful info.

 

Oh, they're fantastic tools. But they read from a relatively thick layer of the surface (even on gold), over a pretty wide area of the surface.

So, maybe that spot is all copper and copper oxides. But that's a layer a few hundred nanometers thick. The XRF gun is reading to a depth of maybe 10 microns, 10,000 nanometers. It's also reading over a spot size of maybe a centimeter, possibly as small as 3mm across if you have the expensive kind. So most of what it will be reading is pure bulk gold, and the spot's composition will be so "diluted" by that surrounding gold that it'll be very hard to read.

All my speculation, of course, as I don't have an XRF gun or a selection of spotted .999 gold coins on hand. But I don't see how it could work any other way.

 

I've spent over an hour with a rep playing with a very expensive model doing all sorts of tests on all sorts of genuine & C/F coins. We did not test a spotted gold coin. I agree, they are nice tools that read a large area.

One day in the future, they may be required at a TPGS for U.S. coin authentication. I'll probably be dead.

For now, I'd want one to identify the composition of ancient and many foreign coins.

 

Okay, now I understand what you're saying but I'm talking about simply authenticating that it is a .999 gold coin. The spots wouldn't matter much to me once, the gold content is authenticated. What I find interesting is that it doesn't happen to all gold buffalo's so what caused it? Was it stored in an unconventional place like under a refrigerator or other uncommon hiding place??

 

Might be interesting to use for ancients, but the best ancient fakes nowadays are melting down real ancients to make the planchets. They got burned too many time with metal composition proving their products were fakes, (traces of modern metals, no traces of impurities that should be in ancient metals, etc). Heck, this was practiced in the late 80's/early 90's and used for the Black Sea hoard.

Like I said, it would still be interesting and valuable to know metal makeup. I also collect early Thai coins, (pre-machinery), and those are FASCINATING to read metal composition.