Published by
Sovereign Gold & Silver Exchange
A stamp can tell you what a piece is represented to be. Testing helps evaluate whether the metal is consistent with that description. The useful question is not just whether a machine gives a reading, but what that reading actually measures.
Sovereign Gold & Silver Exchange uses an Olympus Vanta GX SDD XRF analyzer and a Sigma Metalytics PRO. These instruments provide different kinds of information. Understanding their capabilities and limits is part of understanding the result.
XRF identifies elements near the surface
XRF stands for X-ray fluorescence. The analyzer uses X-rays to produce signals from elements in the area being measured. Those signals allow it to estimate the elemental composition, including precious metals such as gold and silver. The Vanta GX is designed for nondestructive precious-metal analysis and can provide alerts for possible gold plating. [1]
There is an important limit: XRF is surface-sensitive. A reading does not establish the composition of every part of an item. A sufficiently thick coating can hide the material underneath, and a surface reading alone cannot rule out an internal insert. Surface condition and where the measurement is taken can also affect results. [2]
That is why a high gold percentage on one spot should not be treated as proof that an entire bar has the same composition.
Sigma checks electrical resistivity
The Sigma Metalytics PRO evaluates electrical resistivity, a property describing how strongly a material resists electrical current. It compares measurements with the expected response for the selected metal or alloy. It does not use ultrasonic sound waves. [3]
For suitable samples, the PRO's onboard sensors can provide through-sample measurements. Its dimension-verification function uses the entered weight and measured thickness to help check whether the item's dimensions are consistent with the expected density. Sample size, sensor selection, and the correct metal setting all matter. [3]
A Sigma result is a consistency check, not a complete elemental breakdown. It should be interpreted with the item's other characteristics rather than treated as a universal guarantee.
Different checks answer different questions
XRF helps answer, 'What elements are present in the tested surface area?' Sigma helps answer, 'Does the electrical response fit the metal this item is supposed to be?' Weight, dimensions, and visual details provide additional points of comparison. [2, 3]
These checks complement each other. A mismatch deserves investigation, not an explanation chosen just to make the item pass. The appropriate approach depends on whether the item is a recognized bullion product, jewelry, an unknown alloy, or material intended for melting. No single method establishes everything about every piece. [2]
What melt-and-XRF testing means
SGSE's melt-and-XRF service involves melting the material into a bar and taking XRF readings on all six sides. Those readings are averaged for the indicated purity. The stamped information identifies the metal, weight, and XRF-indicated purity, with 'XRF' marked underneath.
Those multiple readings provide information from more locations, but they remain XRF measurements. This service is not a laboratory fire assay. Fire assay uses a different, destructive analytical process. Melting and checking six sides should not be described as laboratory certification or a guarantee of perfectly uniform composition. [2]
Melting also permanently changes the original item. A potentially collectible coin or an item with sentimental value should be considered carefully before choosing that service.
Ask what the result means for your item
Bring your questions about the item and the testing method. Understanding both the result and its limits is more useful than a reassuring number without context.
Call SGSE at 954-834-3429 or visit 1128 US Highway 1, Sebastian, FL 32958, to discuss the appropriate service.
