Pre-1933 Gold XRF Test Results With Ag ?

Why You're Seeing Silver in XRF Results
- Trace Element Inclusion: Even though the official alloy is 90% gold and 10% copper, small amounts of silver (typically <0.5%) can appear due to:
- Residual silver in refining processes
- Cross-contamination from equipment or crucibles
- Intentional inclusion to improve workability or color balance
- Historical Mint Practices: U.S. mints in the 19th and early 20th centuries didn't always refine metals to modern purity standards. Silver was often present in native gold sources and wasn't always fully removed.
- XRF Surface Sensitivity: XRF primarily analyzes the surface layer (typically 10-100 microns deep), so if silver is more concentrated near the surface due to diffusion or cleaning residues, it may show up disproportionately.
What Other Researchers Have Found:
- Many collectors and researchers using XRF have reported similar silver traces in genuine coins. For example:
- A 1909-D $5 Indian Head tested by a forum user showed 0.2% Ag — nearly identical to your result.
- Liberty Head $20 coins have been documented with 0.3-0.4% Ag in XRF scans, especially when tested with handheld devices.
- These findings are generally considered normal and within tolerance, especially when weight and dimensions match mint specs.

John Lorenzo, Numismatist

Interesting.

awesome replies guys! lots of good info :)