Feature Gems & Gemology, Winter 1992, Vol. 28, Issue 4

Methods for Determining Gold Content of Jewelry Metals

Verifying the gold content of karat-gold jewelry is a problem for the entire industry. This study compares four widely available testing methods: density (measured by hydrostatic weighing), chemical reactivity (touchstone testing), capacitive decay (Tri-Electronics G-XL-18 Gold Tester), and X-ray fluorescence (Seiko Instruments SEA 2001 Jewelry Assay System). The latter three methods all proved useful within certain limitations; hydrostatic weighing was least suitable. None of these methods reliably determined gold content within the 3-ppt tolerance allowed by U.S. plumb laws.