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 thin layer (typically 0.5–1.0 mm) of genuine gold 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 gold bars were first widely reported in the late 2000s, when several banks and refineries discovered bars with tungsten cores in their vaults. These were not crude fakes — they had correct serial numbers, proper hallmarks, and had apparently passed through multiple hands without detection.

Tungsten-core coins followed. Reports from dealers and collectors describe professionally manufactured fakes that passed every standard test. Some were only discovered when an owner attempted an assay (destructive analysis), or when an anomalous reading was obtained from an eddy current or conductivity test.

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. The difference is typically 30–60% of the reading, well outside the ±5% authentication tolerance.

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. It works on pure physics and provides an unambiguous pass/fail result that tungsten fakes cannot defeat. Try the free online pendulum simulator, or get the Flat-Pack Pendulum Kit for hands-on testing.