Friday, October 28, 2022

XRF through a slab?

I tried to XRF an archaic Greek coin in an NGC slab.

I got very strange results: LE 97.82%; Ag 2.15% (Silver); Au 0.024% (Gold); Pb 0.010% (Lead)

LE stands for “Lighter Elements”. For this machine, this means Mg, Al, Si, P, and S. (The machine has a way to break this down, but it isn’t my machine, and I didn’t figure out how in the time that I had.)

I gave up after a single test.

According to the blog from a different XRF manufacturer, XRF can be used through slabs. So I decided to take a look at the numbers I got.

If I throw away the LE, and normalize the silver, gold, and lead so they add up to 100%, I get:

------------------ = 98.4% silver
Using similar calculations, gold is 1.1% and lead 0.5%. Those figures are about right for the 3.9g series of “Parion” (actually Thracian) coins.

Perhaps it is possible, with machine settings or calculations like the above, to perform XRF through slabs. Has anyone tried it before and after cracking slabs? Is there a technique that works?

Friday, October 21, 2022

Harlan J Berk catalogs online

Harlan Berk catalogs going back to #1 are online at the Newman Numismatic Portal.

I have had very poor luck searching for them in the NNP search bar, but the link above takes you to the whole set, which can be filtered by year.

The Portal's collection ends with #197. For more recent catalogs, see