Assaying – A science to analyze the purity of gold

How do you know that gold is pure? If you are a jeweler or a metal refiner, ‘Assaying’ is essential to test the gold. It is an assessment that analyses the purity of gold or any other metal object. From jewelry to bullion bars, assay tests are performed on them to determine their value and purity. There are different ways of assaying the metal. Some of them are as below:

1. Stone assay (hand test)Used since ancient times, this is the simplest way to tell the purity of gold. A stone assay is a hard, dark color touchstone with a finely-grained surface. All the jeweler has to do is draw the metal across it, which leaves a visible line. The color of the line determines the purity of the gold.
2. X-Ray Fluorescence (XRF)This assay is much more complicated compared to the stone assay. It tests the purity fast with accuracy, without damaging the metal. Here, the metal is bathed in X-Rays, after which the metal emits fluorescent light at an energy level explicit to the gold’s atomic structure. XRF machine measures the energy levels to determine the purity as well as the percentage of impurities.
3. Fire AssayThough complicated, fire assay is considered as the most reliable and accurate way to test the purity of gold. However, because of its destructive nature, it is usually used for large quantities of bullion. In this method, the metal is mixed with lead oxide and a mixture of fluxes (such as silica and borax), and a reducing agent together at about 1650 F (melting temperature for gold). The lead in the mixture fastens with the gold in the sample. The mixture is then poured into a mold and allowed to cool down. Due to its density, lead sinks at the bottom of the mold. This lead is then reheated in a cupel, a small bone ash container. The lead is absorbed by the cupel, leaving behind the precious metal.
4. Wet AssayingIt includes converting the ore into powder and dissolving it in some acid or mixture of acid. The assayer then analyses the solution chemically. Depending on the metal in question, the assayer uses electrolysis or salts to separate it.The purity of gold is specified by karat. 24-karat gold is the purest. The percentage of gold content is calculated by multiplying it by 4.167 (percent per karat). So, for instance, 18 karat gold has (18 x 4.167) 75 percent gold.

Gold is commonly tested with XRF and fire assays. They are precise and allow the jewelers to make quick and accurate payouts for their customers.

Heritage Gold Capital Holdings, Inc offers a fast efficient melting and assaying service for gold, silver, platinum and palladium as well as Marketing services for gold too.