How Ultrasound Verifies the Authenticity
of Gold and Silver Bullion

Detecting fakes

The enormous and financially destabilizing problem of counterfeit gold and silver bullion is becoming increasingly sophisticated. A gold bar with similar density tungsten inserts or a silver bar containing an equally dense composition of lead, tin, copper or other base metal alloys is able to pass traditional non-invasive tests for authenticity. These tests include density, acid scratching, X-ray spectrometry, and radiography. X-ray fluorescence commonly used by precious metals dealers will not penetrate the surface more than approximately 10 microns, which is about 1/10th the width of a human hair. Thankfully, for investors in bullion, ultrasound technology used by the GT-Ultra Ultrasonic Meter provides the most simple, affordable, and non destructive alternative to drilling into bullion and bars and assaying samples from their cores.

Sound velocity

Ultrasonic detection involves measuring both the velocity of sound in a solid and the distance it travels. Sound velocity is dependent on the elasticity and density of the solid. Together with density testing, differences in sound velocity between precious metals, and the base metals used to counterfeit them, guarantees detection of fakes. GT-Ultra calculates the distance sound waves with a preset velocity travel through a gold or silver bar and echo back to the surface. This distance is compared with the known width of the bar.

Genuine PAMP 10oz gold barFor example, a PAMP Suisse 10oz gold bar has a thickness of 8.3mm. If that bar was comprised of tungsten instead, and the GT-Ultra instrument is pre-selected for the velocity of gold, it would return a measurement of only 5.2mm. The discrepancy represents the proportion that the sound velocity for tungsten (5170 m/s) is faster than the sound velocity for gold (3240 m/s). If the dimensions of the bullion being tested are not known then a vernier calliper or micrometer can be used to measure them. Any result that significantly varies from the known thickness warrants further investigation. GT-Ultra has preset sound velocities for gold, silver, platinum and most of the common base metals and alloys used by counterfeiters. Custom sound velocities for nearly any solid material can be entered into the instrument.

Bullion dealers, Gold Stackers, demonstrate testing of a gold bar using ultrasound

Gold Stackers compare ultrasonic testing of a fake and real silver bar

Wave Reflection

Ultrasonic sound waves emitted from the GT-Ultra transducer will respond to interfaces between different materials when variance in sound velocities cause waves to be reflected. Any unexpected measurements recorded across a single bar may indicate tampering with inserts, thick plating, or voids, and warrants further investigation.

Reflection of ultrasonic sound waves will detect counterfeit gold and silver bullion

Reflection of ultrasonic sound waves detects fake cores and inserts in counterfeit bullion

General Electric demonstrating reflection of ultrasound waves to verify gold bullion