Tungsten Forgery
Also: Tungsten-core fake, Tungsten bar fraud, Tungsten-Core Fake
A tungsten forgery is a counterfeit gold or platinum bar or coin in which a tungsten core is coated with a thin layer of precious metal, exploiting the nearly identical density of tungsten (19.25 g/cm³) and gold (19.32 g/cm³).
The tungsten forgery is considered the most dangerous known method of counterfeiting gold bars and gold coins. The principle exploits a physical coincidence: tungsten (chemical symbol W, Latin Wolframium) has a density of 19.25 g/cm³, almost identical to that of 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 galvanically coated with a gold layer just a few tenths of a millimetre to at most one millimetre thick. The weight, dimensions and external appearance can be reproduced so precisely that even experienced dealers without measuring instruments can be deceived.
Why Tungsten?
Tungsten is the only inexpensive industrial metal that so closely mimics gold in density. For comparison:
| Metal | Density (g/cm³) | Melting point (°C) | Relative price |
|---|---|---|---|
| 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 unsuitable as core materials because their density is far too low – even slight weight deviations are immediately apparent. Tungsten, on the other hand, requires sophisticated measurement technology to be exposed.
How Are Tungsten Forgeries Made?
Technically, two main methods are described:
- Drilling and filling: A genuine gold piece is hollowed out from the inside, filled with tungsten, and the opening is resealed, polished and finished.
- Tungsten core with gold plating: A precisely machined tungsten piece receives a gold coating by electroplating or roll-bonding, which is then stamped or cast.
Particularly insidious: an acid test or streak test on the surface only tests the gold layer itself – the tungsten core beneath remains completely concealed. Since tungsten's melting point of 3,422 °C is far above that of gold (1,064 °C), a simple melt test for identification is also ruled out.
Reliable Testing Methods
The coin authenticity checker and the coin weight checker are good first steps, but are not sufficient for bars. The following methods reliably detect tungsten forgeries:
- Ultrasound testing (ultrasonic reflectometry): sound waves are reflected at the boundary layer between the gold coating and the tungsten core – the most precise non-destructive method for bars.
- X-ray fluorescence analysis (XRF): measures the elemental composition in multiple depth layers; detects tungsten cores beneath thin gold coatings.
- Density determination by Archimedes: weighing in water determines the precise volume; in tungsten bars, the measured density deviates slightly from 19.32 – however, a very precise laboratory scale is required.
Density = weight in air / (weight in air − weight in water) × density of water
- Magnet test: tungsten is weakly paramagnetic, gold is diamagnetic – a neodymium magnet shows no measurable attraction to pure gold.
- Ping test: gold coins produce a characteristic long-lasting tone; tungsten significantly dampens the sound.
- Sigma Metalytics / multi-spectrum eddy current: professional devices measure electrical conductivity through the gold layer – tungsten has a significantly lower conductivity than gold.
Which Products Are Particularly at Risk?
Tungsten forgeries have so far been documented primarily in 1-kg gold bars and large bar denominations. Smaller units such as 1-ounce gold bars or bullion coins are more difficult to fake, but do also occur. Coins with finely struck security features (micro-engraving, edge lettering, holographic certificates) offer enhanced protection.
When purchasing, one should buy exclusively from dealers with LBMA Good Delivery certification and insist on complete documentation (serial number, assay certificate).
In Brief
Tungsten forgeries are technically the most sophisticated gold counterfeits of all and are virtually undetectable with the naked eye or a simple scale. Anyone buying or accepting larger bars should insist on ultrasound or XRF testing – or buy exclusively from certified dealers with authenticity certificates.