Tungsten Forgery
Also: Tungsten-filled fake, Tungsten bar fraud, Tungsten-core counterfeit
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 almost identical density of tungsten (19.25 g/cm3) and gold (19.32 g/cm3).
The tungsten forgery is widely regarded as the most dangerous known technique for faking gold bars and gold coins. The whole method rests on a quirk of physics: tungsten (chemical symbol W) has a density of 19.25 g/cm3, almost exactly matching that of gold at 19.32 g/cm3. The gap is under 0.4 % - far too small for an ordinary balance to flag reliably.
Faked bars usually consist of a tungsten core plated or electro-deposited with a gold skin only a few tenths of a millimetre to at most one millimetre thick. Weight, dimensions and external appearance can be reproduced so faithfully that even seasoned dealers are fooled without measuring instruments.
Why tungsten?
Tungsten is the only inexpensive industrial metal that mimics the density of gold so closely. By way of 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 minor weight discrepancies stand out immediately. Tungsten, by contrast, demands sophisticated measurement equipment to expose.
How are tungsten forgeries made?
Two main methods are commonly described:
- Drill and fill: a genuine gold piece is hollowed out from the inside, packed with tungsten, and the opening is resealed and polished.
- Tungsten core with gold overlay: a precisely machined tungsten piece is given a gold coating by electroplating or roll cladding, which is then struck or cast.
Especially treacherous: an acid test or a streak test only examines the surface gold layer itself - the tungsten core underneath stays completely hidden. Because tungsten melts at 3,422 C, far above gold's 1,064 C, a simple melt test is also useless for identification.
Reliable testing methods
The coin authenticity check and the coin weight verifier are sensible first steps, but they are not enough for bars. The following methods expose tungsten forgeries with confidence:
- Ultrasound testing (ultrasonic reflectometry): sound waves reflect off the interface between the gold overlay and the tungsten core - the most precise non-destructive method for bars.
- X-ray fluorescence analysis (XRF): measures the elemental composition across several depth layers, revealing tungsten cores under thin gold skins.
- Density test by Archimedes: weighing in water yields the exact volume; for tungsten bars the measured density drifts slightly from 19.32, though this requires a very accurate laboratory balance.
Density = weight in air / (weight in air - weight in water) x density of water
- Magnet test: tungsten is weakly paramagnetic while gold is diamagnetic - a neodymium magnet shows no measurable pull on pure gold.
- Ping test: gold coins ring with a characteristic long tone; tungsten noticeably dampens the sound.
- Sigma Metalytics / multi-spectrum eddy current: professional devices measure electrical conductivity right through the gold layer - tungsten conducts far worse than gold.
Which products are most at risk?
Tungsten forgeries have so far been documented above all in 1-kg gold bars and large bar denominations. Smaller units such as 1-ounce gold bars or bullion coins are more laborious to fake but do occur. Coins with finely rendered security features (micro-punching, edge lettering, holographic certificates) offer added protection.
When buying, stick to dealers with LBMA Good Delivery certification and insist on complete documentation (serial number, assay certificate).
In short
Tungsten forgeries are the most technically sophisticated gold fakes in existence and are barely detectable by eye or with a simple scale. Anyone buying or accepting larger bars should insist on ultrasound or XRF testing - or buy only from certified dealers who supply a certificate of authenticity.