Tungsten Counterfeit
Also: tungsten fake, tungsten bar fraud, tungsten-core fake
A tungsten counterfeit is a fake gold or platinum bar or coin in which a tungsten core is coated with a thin layer of precious metal, exploiting the almost identical density of tungsten (19.25 g/cm³) and gold (19.32 g/cm³).
The tungsten counterfeit is considered the most dangerous known method of imitating gold bars and gold coins. The principle exploits a physical coincidence: tungsten (chemical symbol W, from the Swedish tung sten, "heavy stone") has, at 19.25 g/cm³, almost the same density as gold (19.32 g/cm³). The deviation is less than 0.4 % — far below what a simple scale can reliably detect.
Counterfeit bars typically consist of a tungsten core plated or electroplated with a gold layer only a few tenths of a millimetre up to a maximum of one millimetre thick. Weight, dimensions and external appearance can be reproduced so exactly that even experienced dealers can be deceived without measuring instruments.
Why tungsten?
Tungsten is the only low-cost industrial metal that imitates gold's density so closely. For comparison:
| Metal | Density (g/cm³) | Melting point (°C) | Price (relative) |
|---|---|---|---|
| Gold | 19.32 | 1,064 | very high |
| Tungsten | 19.25 | 3,422 | low |
| Lead | 11.34 | 327 | very low |
| Copper | 8.96 | 1,085 | low |
| Platinum | 21.45 | 1,768 | very high |
Lead or copper are ruled out as core materials because their density is far too low — even small weight deviations are immediately noticeable. Tungsten, on the other hand, requires sophisticated measuring technology to expose.
How are tungsten counterfeits made?
Two main methods are described technically:
- Drilling and filling: a genuine gold piece is hollowed out from the inside, filled with tungsten, and the opening resealed and polished.
- Tungsten core with gold cladding: a precisely milled tungsten piece is given a gold cladding by electroplating or roll bonding, which is subsequently struck or cast.
Particularly insidious: an acid test or streak test on the surface checks only the gold layer itself — the tungsten core underneath remains completely hidden. Because tungsten's melting point of 3,422 °C lies far above that of gold (1,064 °C), a simple melt test is also ruled out for identification.
Reliable testing methods
The coin authenticity check and the coin weight checker are good first steps, but are not sufficient for bars. The following methods reliably expose tungsten counterfeits:
- Ultrasonic testing (ultrasonic reflectometry): sound waves are reflected at the boundary layer between gold cladding and tungsten core — the most precise non-destructive method for bars.
- X-ray fluorescence analysis (XRF): measures the elemental composition at several depth layers; exposes tungsten cores beneath thin gold layers.
- Density measurement using Archimedes: weighing in water determines the exact volume; for tungsten bars the measured density deviates slightly from 19.32 — but this requires a very precise laboratory scale.
Density = weight in air / (weight in air − weight in water) × density of water
- Magnet test: tungsten is weakly paramagnetic, gold diamagnetic — a neodymium magnet shows no measurable attraction on pure gold.
- Ping test (sound test): gold coins produce a characteristic long tone; tungsten noticeably dampens the sound.
- Sigma Metalytics / multi-spectrum eddy current: professional devices measure the electrical conductivity through the gold layer — tungsten has a considerably lower conductivity than gold.
Which products are particularly at risk?
Tungsten counterfeits have so far been documented above all in 1 kg gold bars and large bar denominations. Smaller units such as 1 oz gold bars or bullion coins are more laborious to fake, but do occur. Coins with finely executed security features (micro-dotting, edge lettering, holographic certificates) offer increased protection.
When buying, one should purchase exclusively from dealers with LBMA Good Delivery certification and insist on complete documentation (serial number, assay certificate).
In brief
Tungsten counterfeits are the most technically demanding gold fakes of all and are scarcely detectable with the naked eye or a simple scale. Anyone buying or accepting larger bars should insist on ultrasonic or XRF testing — or buy exclusively from certified dealers with an authenticity certificate.