Fake gold bars: the tungsten that fools the scales

Fake gold bars: when weight and measurement are not enough

A solid gold bar is not what it seems. The news of a 10-ounce bar filled with tungsten found in the heart of Manhattan's jewelry district raised an uncomfortable problem for anyone holding physical metal: counterfeiting can no longer be detected with the old methods. Tungsten has a density of 19.25 g/cm³ compared with gold's 19.32. The difference is so small that a bar can show the exact weight, the exact volume and, therefore, the same Archimedes displacement. The scale stays silent. The caliper stays silent.

The first serious warning came with coins. In one-ounce pieces minted in 22-karat gold, inserting a tungsten core without altering weight and diameter is practically impossible: the resulting alloy would be lighter or thicker. There, counterfeiting gives itself away if one bothers to measure. The problem lies with cast bars, where the case, the blister pack and the serial number do the work of convincing the buyer. A pretty wrapper certifies nothing.

What a neodymium magnet detects and what it does not

The property that breaks the disguise is magnetism. Gold is diamagnetic: it slightly repels a magnetic field. Tungsten is paramagnetic: it allows itself to be attracted. A sufficiently strong neodymium magnet brings the test within reach. On an authentic coin nothing sticks; on a piece with a tungsten core, it does. The nuance matters: you need a strong magnet and a very thin plating layer for the reaction to be visible. With a light bulb filament, the homemade demonstration is misleading, because the filament moves due to heat and current, not because of gold's diamagnetism.

Some have taken the experiment further and bought a plated tungsten ring to check its behavior with magnets. The result confirms the suspicion: tungsten responds, gold does not. The catch is that the method requires some practice and does not distinguish a legitimate piece from an osmium or platinum alloy, which are also paramagnetic and have similar densities.

The kit sold as a solution and what it costs

The market offers specific gadgets. The most advertised is the Fisch, a template that checks the diameter and thickness of specific coins. A single unit costs around 169 dollars plus shipping; buying five cases at once brings the unit price down to about 90 dollars. The cheap alternative is a balance scale with slots for different coins, which mixes 22- and 24-karat pieces and does not solve the case of sovereigns. For small bars, the recommendation that keeps coming up is the kinebar, with its built-in hologram, or going directly to a fruta refinery with certificate and invoice.

---

The point where everything gets stuck is the same as at the beginning: a bar can weigh what it should, measure what it should and still not be gold. The only solid defense remains traceability. And that is not provided by a magnet.