Why Tungsten Is the Perfect Counterfeit Material

Tungsten has a density of 19.25 g/cm³. Gold has a density of 19.30 g/cm³. The difference is just 0.26% — well within the measurement error of most consumer-grade density tests. This near-perfect density match makes tungsten uniquely dangerous as a counterfeiting material.

No other common metal comes close. Lead is too light (11.34 g/cm³), platinum is slightly too heavy (21.45 g/cm³), and depleted uranium, while close in density, is radioactive and controlled. Tungsten is cheap, widely available, and non-toxic. A tungsten blank costs a fraction of the gold it imitates.

A tungsten core plated with a gold layer will have the correct total weight, the correct displacement volume, and therefore the correct specific gravity. Standard density testing — the Archimedes method of weighing in air and in water — simply cannot tell the difference.

A precision scale shows the correct mass because the coin is manufactured to the exact specified weight. Digital callipers show the correct dimensions. The acid test reads positive because the surface is real gold. XRF (X-ray fluorescence) analysis — used by many professional dealers — only penetrates 10–20 micrometres into the surface, well within the gold plating layer.

The magnet test fails because tungsten, like gold, is non-magnetic. The coin slides down a tilted magnet at the correct rate. Visual inspection is futile against well-made fakes that use genuine coin dies or high-quality replicas.

Even ultrasonic thickness testing, sometimes suggested as a solution, can be defeated by careful layering. The counterfeiter’s craft has advanced to the point where the only reliable detection method must measure a bulk physical property that differs fundamentally between gold and tungsten.

Tungsten-filled bars and tungsten-core coins have been reported by dealers and collectors. Some were found only when an owner had the metal assayed (destructive analysis), or when a conductivity test gave an unexpected reading.

The scale of the problem is unknown because detection is difficult. Many fakes may be sitting in vaults and safe deposit boxes, their owners unaware. This is precisely why non-destructive authentication methods that can detect bulk conductivity differences are so important.

While tungsten matches gold’s density, it cannot match gold’s electrical conductivity. Pure gold conducts electricity at 44.0 MS/m (megasiemens per metre). Tungsten conducts at only 17.9 MS/m — less than half. This 2.5:1 ratio is a fundamental physical property that cannot be altered without changing the material itself.

Eddy current testing exploits this difference. When a strong magnet swings past a coin, it induces circulating electrical currents in the metal. These eddy currents create their own magnetic field that opposes the magnet’s motion, slowing it down. The amount of slowing depends directly on the conductivity of the material.

A genuine gold coin damps the pendulum to a specific angle. A tungsten-core fake produces significantly less damping because its bulk conductivity is lower. The gold plating is too thin to generate sufficient eddy currents to compensate for the tungsten core. In the model, a gold-plated tungsten fake reads about 2.4 times a genuine fine-gold coin and about half a genuine Krugerrand, outside both the ±5% reference-coin band and the ±21% formula band. This is modelled, not measured on a fake.

The best defence against tungsten counterfeits is a multi-factor authentication approach. Start with visual inspection and dimensional verification to catch crude fakes. Use an acoustic ping test to check the internal resonant frequency. Then use an eddy current test to verify bulk conductivity.

When buying gold privately or through peer-to-peer platforms, insist on authentication data. A seller who can provide eddy current readings, ping test results, and dimensional measurements demonstrates that their gold has been properly verified.

EON’s eddy current testing method is specifically designed to detect tungsten-core counterfeits. In the model, a plain tungsten core is clearly separated; engineered layered fakes of 22-carat coins can come close. Try the free online pendulum simulator. The Flat-Pack Pendulum Kit is in development; prototypes have not yet been tested.