The problem of testing gold jewellery

Authenticating gold jewellery is a major challenge. Due to the very diverse geometries (rings, necklaces and ear studs, etc.) and the composition (different mixed gold alloys in different carats), it is impossible to determine gold jewellery exactly using only one test method. The most common types of counterfeit jewellery are

• Counterfeit jewellery with base metals: This refers to the plating of a base metal with gold. This often occurs with rings or chains made of tungsten or tungsten carbide, whereby these materials almost perfectly imitate the density and thus the “heavy feeling” and feel of real gold jewellery.
• Under-alloying / hallmark fraud: If the gold content of an alloy is lower than specified by the hallmark.
• This can also be done in an even more sophisticated way, in that the surface of the piece of jewellery has the correct alloy and the underlying material is worthless foreign material or an inferior alloy.

Due to the large number of different types of gold alloys and jewellery geometries, the testing of jewellery is more demanding than that of gold bars, for example. The following testing methods should therefore be available when purchasing jewellery.

1. magnetic scale "MagneticScreenScale "
A sustainable method for measuring bars and coins is to determine the so-called magnetic susceptibility properties. This makes it possible to determine, even through blister packs and packaging up to a certain thickness, whether the material applied has the correct magnetic behaviour - para- or diamagnetic, i.e. attractive or repulsive. A so-called “tungsten detector” can be used to determine the presence of a potential foreign body: a gold bar as a so-called diamagnet displaces a magnetic field, creating pressure on the measuring head of the scale and displaying a positive value. If a supposedly genuine fine gold bar is placed on the scale and a negative value appears, it is in most cases a fake.

2. density scale "DensityScreenScale "
You can use the density scales to quickly and precisely determine the density of all types of materials. It is equally suitable for analysing bars and gold jewellery to determine their purity and alloy composition and to determine bars or jewellery that have been “stretched” or under-alloyed with silver or copper. The density is determined using the tried and tested method of Archimedes: To do this, the object is weighed with a sieve under water and once “normally”. The density can be determined directly from the two different values. This gives you an insight into the quality and carat of the gold or even an initial indication of the possible presence of forgeries. Determining the authenticity and gold content of geometrically irregular objects such as jewellery is therefore no problem.

3. surface testing with test acids or X-ray fluorescence analysis

• The gold coating sample with test acids: In principle, the first, relatively simple and cost-effective step is to determine the gold content using gold test acids.
• X-ray fluorescence analysis (XRF): This determines the exact elemental composition of the jewellery on the surface. This method is very expensive (approx. 15,000 - 45,000 EUR) and is purely superficial: the maximum penetration depth is only 0.010 mm.

Electrochemical testing using the "CaratScreenPen ".
The CaratScreenPen uses an electrochemical process to determine the purity and fine gold content on the surface of gold and platinum jewellery. The measuring tip forms a so-called “galvanic cell” on contact with the object lying on the measuring surface. This results in a certain electrochemical behaviour, which is registered by the measuring tip and processed by the device.

The complete and detailed article on the methods of gold testing can be found here: