Analyze this: Why testing metal content matters
by jacquie_dealmeida | May 1, 2016 9:00 am
By Jonathan Margalit
The jewellery you just bought from a stranger looks like gold and acid tests might even indicate that’s what it is. But are you sure? More and more, jewellers are falling victim to a scam involving a metal alloy similar to stainless steel.
Even in the face of decades of experience, veteran jewellers are being duped by this unpleasant and downright costly trick.
The scam rarely deviates from the following. A suspect enters a jewellery store or pawn shop with what they allege is an 18-karat gold bracelet, necklace, or ring, hoping to sell it for cash. Since most jewellery consists of either 14-karat or 18-karat gold, a con artist is likely to maximize his profit by trying to sell a piece that looks to be 18-karat. The higher the ‘detected’ karat value, the bigger the criminal’s cashed-in ‘profit.’
The jeweller performs an acid test, which usually identifies the metal as 18-karat gold and a transaction ensues. (Interestingly, a further test with a 22-karat gold acid may reveal the piece is indeed gold-plated stainless steel.) Believing the item is truly 18-karat gold, the jeweller purchases the piece and the criminal walks away with hundreds, even thousands, of dollars.
The root of the problem is many jewellers rely on acid tests to determine the authenticity and karat value of the item in question. Purchased for up to $50 per kit, acid tests are a common and accepted practice to help determine the approximate karat value of precious metals, such as gold. By their nature, these tests are qualitative and can have limited accuracy.
The test works by applying a series of acids—which are corrosive and require the jeweller wear special protection—to determine karat range, namely, those between 10-, 14-, 18-, and 22-karat gold. Based on the chemical reaction that takes place, or the lack thereof, the user may conclude the karat value of a jewellery item lies within a certain range (e.g. above 14-karat and below 18-karat). What the test does not reveal is the actual gold concentration, the existence and concentration of other precious metals, or whether the piece is gold-plated. The acid test is, to a certain degree, destructive, and by no means acceptable when evaluating high-value items, such as numismatic coins.
Typically priced between $100 to $1000, electronic precious metals testers are another tool jewellers commonly use. This technology measures the electrical conductivity of gold in a piece of jewellery and can serve as an indicator for its gold content. Although electronic testers can provide an answer quickly, they are limited to the types of precious metals that can be detected (i.e. typically gold and platinum) and may be less accurate with high-karat items. In addition, they may produce false results due to possible cross-contamination of the testing probe.
While fire assays are very accurate, they can be complicated to carry out, requiring trained and experienced operators. They are also destructive in the sense the piece being tested is melted. The gold, however, can be fully recovered.
Another option—advanced X-ray fluorescence (XRF) technology—can allow jewellers to perform a quick, non-destructive, and accurate analysis of jewellery, coins, and other items containing precious metal.
XRF can identify the composition of a sample by reading characteristic X-rays of the various elements (or ‘fingerprint’) within a metal. Its non-destructive method can analyze all precious metals and common alloying elements, including gold, silver, platinum, and palladium, as well as common elements used in counterfeiting of precious metal alloys, such as chromium, titanium, and tungsten. Devices of this nature display the sample’s chemical composition. In the case of gold, they can also determine karat value.
In addition, one XRF device equipped with a patented gold-plating detection technology performs a series of primary and secondary tests to flag gold-plated items; it works regardless of the composition of the substrate or the plating layer.
Compared to some of the traditional methods used to evaluate precious metals in jewellery, portable XRF is typically priced higher than acid test kits or electronic testers. However, depending on the volume and type of jewellery being traded, the payback period may be less than a year for some users.
There are several commercial methods used to determine the true value and authenticity of jewellery. Although the cash-for-gold craze has tapered somewhat due to lower gold prices, jewellers and others who trade in precious metals must adopt a testing method that is cost-effective and appropriate for their operation. In the final analysis, protecting your interests is of the utmost importance.
Jonathan Margalit is the business development manager for Thermo Scientific Portable Analytical Instruments, a business unit within Thermo Fisher Scientific. In his role, Margalit manages the development of new precious metals and metal-recycling markets and applications. He received his PhD from the RWTH Aachen, Germany, in the field of high-temperature aircraft ceramics.
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