XRF Results - 1812 And 1813 Zacatecas 8 Reales

10.7 seems too much to me.

Remember, SG is the whole coin. XRF is just the small bit hit by the beam.

Please keep us posted when you get the new XRF readouts. By the way, very nice 1812, that coin is hard to find where it can even be identified.

Agree ... the instrument should be capable for Au.
Personally, I would always take an XRF result over SG, though (as pointed out by others) would take several XRF measurements.

Regardless, interesting results, thanks for sharing.

Thank you! Before I bought it I briefly thought of holding out for a better condition piece, but I had read Max Keech's article describing the 1812 draped bust as "rock bottom" for quality of Zacatecas output, lol. So I'm glad I picked it up as a better one sounds hard to come by and likely would be priced accordingly.

Thanks all for the XRF input. I haven't had a ton of coins tested so far, I'm interested to see more results. Not sure if the testing is rigorous enough to draw any concrete conclusions but I'm havimg fun.

Based on over 200 XRF tests run to date, I believe the necessity of a gold trace cannot be avoided on coins minted in Mexico. The parameters for Peru and Bolivia are different but can also be identified. SG along with XRF is critical as long as good lab procedures are in place. I learned how to do SG in High School and it has not changed in the 60 plus years since. The entire mother lode and adjacent veins in Mexico all have a detectable amount of gold in them. The denser metals are definitely easier to detect than the lighter ones. These are all simple scientific facts. These are published in articles and books on authentication.

A coin made in 1812 in Mexico has to contain gold. It comes with the silver period.

Now lead is a horse of a different color. Argentiferous lead is quite rare in Mexico. It is very common, in fact normal, for deposits in the UK and Europe to be argentiferous lead. Check when and where the Mexican deposits of this type were being refined and you will see that none are identified as early as 1812. The signature of the alloy may indicate an English numismatic forgery. Either or both could be.

Regarding a higher-than-expected SG, I have seen revolutionary era coins at 10.4 but none higher in my experience doing tests. I have heard of coins as high as 10-12% gold but I have not personally tested any of these. It is however theoretically possible based on modern core sample test results to find deposits that would be that high.