1912-S Lincoln Cent: Improper Mix (Unmelted Fragments) or Strike through metal fragments?

Cool results!

Steve

 

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I've seen a very few number of these
with (apparently) attributed gold flakes
or a strip like this.

The San Francisco Mint was striking $5 Indians
and $10 Indians that year, so I suppose anything
is possible.

In general, however, the Mint(s) tried to keep the
gold coin area well away from cents thru higher
denominations. I obviously don't know how far
away the Gold presses were from the Cent presses
back then.......

If from a coin, the source would normally be expected
to be from a detached piece of lamination - either
before or after striking .......this would be 'before striking'
imo, if that is indeed the source. Almost impossible to
determine, imo

 

I guess it remains a mystery.

Fred, if I were to submit this for examination, is this something that they could determine for certain with it in hand?

The other thing I wondered is why isnt the copper close to 95%? He scanned it twice. Came back 82%.

How can that be explained?

 

What was the analysis area in comparison to the size of the rolled in foreign material? I assume it would encompass a larger area then just the foreign metal, so you are combining the chemistries of the foreign metal and the coin into one analysis which is then weighted to 100%. Also, XRF is only a surface chemistry. I would expect there to be oxygen present due to oxidation, but I do not believe that oxygen is detectable on the XRF and it was not included in the analysis report.

With SEM/EDS, you can zoom in and analyze only the foreign metal, so that will give you a more accurate chemical analysis.

 

Since it isn't an SEM, I can't answer any of your questions.

 

@JCro57 I agree with @mithril21 The field of analysis on the handheld XRF units is dependent on the operator and the topography of the sampled area. In addition, the algorithm that calculates the comp based on the peak heights may not be as good as those in Lab equipment. SEM/EDS would be much better IMO, but it's going to cost at least $100 and maybe more. (I had a buddy that was a post doc in the chem dept at UB, but he is long gone). I think the fact the the handheld XRF showed gold is very promising, however.

Bottom line, I think it's going to cost a few bucks to get the applicable data to prove its a gold inclusion. The question is whether the cost is justified. FWIW, I think it's gold based on the analysis, but my opinion and $2 will get you a coffee at Tim Hortons

 

The Fischerscope X-ray Xan 250 is a benchtop XRF instrument, not a handheld XRF. This is considered quantitative and highly accurate because each element is calibrated to standards. SEM/EDS is non-standard based and considered “semi-quantitative.” However, for this particular application, SEM/EDS is the superior method because of the size of the foreign metal.

The element range on the XRF is Al - U, so it cannot detect the oxygen on the surface from over 100 years of oxidation. The oxidation changes the surface chemistry of the coin. One reason why the copper is less than 95%. EDS can detect oxygen, although it is not highly accurate.

The smallest measurement spot size on this XRF unit is 0.3 mm diameter, depending on the measuring distance and the aperture. However, the spot size is typically closer to 3-5 mm diameter for these instruments using the standard size aperture. This is larger than the size of the foreign metal, so you are getting both chemistries combined into one which is then weighted to 100%. Another reason why it shows copper is less than 95%. EDS can have a spot size down to just a few microns.

The analysis does indicate the presence of gold, so I do not doubt the foreign metal contains gold.

If you live near southern Indiana, then I may be able to perform the SEM/EDS analysis for you if you want.

 

I appreciate it, but I live in Buffalo.