Gold reference standard?

[kat...@otenet.gr]

Hi everyone,

I have been analyzing archaeological gold alloys using a Bruker 5i and the Precious Metals calibration; mostly gold/silver alloys (33-88% Au) with small amounts Cu (0.3-3.7%), according to the calibration.

I would like to check the accuracy of the measurements by using one standard reference sample for a gold/silver alloy with low Cu. I can't find one! Does anyone have a recommendation about where to look? (I did use the sterling silver coupon provided with the unit which gave me a δ relative % of 11.42%).

The only thing I found was a reference to the use of home-made reference samples here..

Guerra, M. F., & Tissot, I. (2016). Bronze Age and Iron Age gold torcs and earrings from the Iberian Atlantic façade: a non‐invasive multi‐analytical approach to the characterisation of the alloys and the corrosion. X‐Ray Spectrometry, 45(1), 5-13.

Any ideas?

Kathy Hall

[Branden Rizzuto]

Hi Kathy,

You may want to check out the “Gold Jewelry Alloy for Handheld XRF Instruments Application” standards provided by FLUXANA and also ERM-EB506, ERM-EB507, and ERM-EB508 produced by BAM. Note though that some of these standards contain nickel, zinc, and/or palladium in significant quantities, reflecting the compositions of more modern gold alloys rather than ancient/historical gold alloys.

Cheers,

Branden

--
Visit the pXRF for Cultural Heritage website at:
https://sites.google.com/site/pxrfgroup/
---
You received this message because you are subscribed to the Google Groups "pXRF for Cultural Heritage" group.
To unsubscribe from this group and stop receiving emails from it, send an email to pxrf+uns...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/pxrf/633dab91-e16f-4956-8b3c-442f4b2a1526n%40googlegroups.com.

[Mark Rasmussen]

Hello Kathy,

I really enjoy following these threads and thought I would jump in :-)

As you look for more quantitative vs. qualitative results, you may want to perform some simple tests to further explore some of the considerations/issues.

1) Take a piece of copper foil (the thinnest you can get) and place it on some gold (e.g., gold coin) and analyze it. What is the percentage of copper/gold?

2) Take a piece of copper foil (the thinnest you can get) and place it on some iron and analyze it. What is the percentage of copper/iron?

3) Take a gold leaf sheet (the thinnest you can get) and place it on some iron and analyze it. What is the percentage of gold/iron?

4) Take a gold leaf sheet (the thinnest you can get) and place it on a thick piece of copper and analyze it. What is the percentage of gold/copper?

5) Take a silver leaf sheet (the thinnest you can get) and place it on some iron and analyze it. What is the percentage of silver/iron?

6) Take a silver leaf sheet (the thinnest you can get) and place it on some gold (e.g.,  gold coin  ) and analyze it. What is the percentage of silver/gold?

7) Take a silver leaf sheet (the thinnest you can get) and place it on a thick piece of copper and analyze it. What is the percentage of silver/copper?

8) You can laminate/stack some foil sheets etc. and analyze the edge (within the spot size) and raise some interesting questions.

Testing metals or surfaces that result from inhomogeneous castings or depletion gilding (e.g., tumbaga), mercury gilding, fire gilding, electroplating, and physical vapor deposition et al. should raise the same questions.

Further research (e.g., Google Scholar, Getty metals publications, or AIC RATS resources):

Peter Northover has written on Electron probe microanalysis (EPMA) and X-ray fluorescence (XRF) in relation to these considerations/issues.

Hector Neff has written on ICP-MS in relation to these considerations/issues.

David A. Scott has provided great insights into these considerations/issues.

W. T. Chase - Tom has provided great insights into these considerations/issues.

Paul T Craddock covers techniques and limitations in Scientific Investigation of Copies, Fakes and Forgeries (https://www.amazon.com/Scientific-Investigation-Copies-Fakes-Forgeries-ebook/dp/B0B5GCY6XT)

Ernst Pernicka has made some significant contributions in this area as well as in the development of complementary testing methods (e.g., Pb-210 testing).

Respectfully,

Mark Rasmussen

To view this discussion on the web visit https://groups.google.com/d/msgid/pxrf/CAG0Pr76ZdxPkD6mqE24z%2B0PiM9A%3DSZAGygjFKqKg_S%3DJGL68Lw%40mail.gmail.com.

[kat...@otenet.gr]

Thanks for your replies.

Mark; to calculate information depth, Bruker recently directed me here: https://xrfcheck.bruker.com/InfoDepth

I will add to the list of references Eleanor Blakelock's interesting work on depletion gilding in the Staffordshire Hoard.

For the standards, perhaps the ideal would be to have one of these modern ones, but also to create a closer matching set using unprovenanced old material which has been analyzed using a more precise technique. I suppose this is what is meant in the paper by 'home-made' samples. Sounds like a fun project..

Kathy

[Alexander Seyfarth Mineralogical Analysis]

Hi

Au reference samples can be achieved from the following sources:

a) FLUXANA: specially certified 16mm disks mounted on a resin substrate. Also used by all vendors for their calibrations

FLUXSEARCH; register and then you can search and get Part Number and quote or easier in the USA via BRAMMERSTANDARDS in TEXAS.

FLX 0732-16a

FLX 0734-16a  

FLX 0720-16

Others are not longer available

b) German BAM

ERM 506, 507, 508 

c) Other options:

Use some of your Jewelry  with a hall mark to determine the Au content; e,g. 18K and 22K ; This will show you also the right way to position the sample (make sure to have the widest part in the direction of beam and detector).

d) Making your own … or ask a professional Jewelry professional to melt from material… This is complex and not easy to make a homogeneous sample as the analyzed layer for Au, Cu and Zn is not very large …

In the old days my team made the calibration and it is designed more for current alloys then archeological setups but will work with lower range Au and higher Cu. The cut off will be 8K Gold.

Hope this helps!

Alexander Seyfarth

--
Visit the pXRF for Cultural Heritage website at:
https://sites.google.com/site/pxrfgroup/
---
You received this message because you are subscribed to the Google Groups "pXRF for Cultural Heritage" group.
To unsubscribe from this group and stop receiving emails from it, send an email to pxrf+uns...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/pxrf/633dab91-e16f-4956-8b3c-442f4b2a1526n%40googlegroups.com.

Alexander Seyfarth Mineralogical Analysis

miner...@gmail.com

Janesville USA