One of the factors that many gold stackers and collectors consider when purchasing coins and bars is their purity. But how is this purity determined, and how is gold assaying involved? A gold assay is a process to measure the purity of items containing gold. The primary purpose of gold assaying is to ensure that gold coins, bullion bars, or other gold items meet specific standards of purity and are not fraudulent or of lesser value than they should be. Keep reading to learn more about the various methods for assay gold testing, what factors affect gold assay results, and more!
What is the Process of Gold Assaying?
Gold assaying is the process of determining the purity and content of gold in a sample, which is an essential step in the gold mining, refining, and jewelry-making industries. The assaying process involves a series of analytical techniques to measure the gold content in the sample accurately. There are a few gold assay processes that measure the purity of gold, including fire assay, X-Ray assay, and atomic absorption spectroscopy.
What is Fire Assay For Gold?
Fire assay is the oldest method of gold testing. This method employs a combination of intense heat (1900 °F) produced by a furnace, bone ash containers called crucibles and cupels, and dry reagents called fluxes. This method works because all samples tested by this process must be soluble in molten metallic lead, with gold and silver being insoluble in slag. The process depends on the differences in density among the molten lead, the slag, and the liquids, with gravity ultimately separating the alloy from the slag. This method of assaying must be carried out by those proficient in the process to produce reliable results. The results of the process are calculated using a standard measurement unit known as an assay ton.
What is X-Ray Assay For Gold?
X-ray assay gold testing is another popular way to test the purity of gold. This method is carried out by specialized machines that bathe samples in X-rays. The metal emits fluorescence at an energy level determined by its atomic structure. The devices then give a reading of the purity of the sample with a high degree of accuracy that is measured in parts per thousand.
What is Atomic Absorption Spectroscopy For Gold?
A third method of gold assay testing involves atomic absorption spectroscopy. This method uses characteristic wavelengths of electromagnetic radiation from a light source and can be used to test both solid and liquid samples. This method works because atoms of individual elements absorb different radiation wavelengths. The process starts with analytes being atomized so that their characteristic wavelengths get emitted, and those wavelengths are recorded. During excitation, electrons in individual atoms jump up a level as the atoms absorb a specific energy, which is determined by the particular wavelength that varies by element. Therefore, the concentrations of specific elements can be determined using the proper wavelength and intensity.
What Are The Factors That Affect Gold Assay Results?
A variety of factors can impact the purity of gold. Among them are impurities, contamination, and preparation techniques. When mined, most gold is about 85% pure, but the variation ranges from 65% to 98%. Gold extracted through the processes of amalgamation or cyanidation may have any number of impurities, such as iron, copper, and zinc. Gold is sometimes intentionally mixed with other elements, such as silver, because gold is the most malleable metal on the periodic table, and gold alloys are less prone to damage.
Even gold nuggets are never 100% pure. Limestone, quartz, and iron are a few examples of things found on a matrix of gold nuggets. They, however, are not part of the metal itself. Instead, gold nuggets are alloys. The most common element alloyed with gold is silver, and some gold nuggets may be a fifth silver or more, in which case they are technically considered electrum rather than gold.
How to Understand Gold Assay Results?
The results of gold assay tests are measured in karats, which can then be converted into percentages. A karat is 1/24 of the total material comprising an object. This definition means that 18 karat gold would indicate that the gold is 18/24 gold, or 75% pure gold, while 24 karat gold would indicate that the gold is 24/24 gold, or .9999+ pure. This method of measurement means that if two gold items have the same weight, but one is 18 karat gold, and one is 24 karat gold, the latter technically contains more pure gold than the former.
Should I buy gold in Assay?
Gold is sometimes sold “in assay.” Assay gold cards are gold bars sealed intact packaging that includes an assay gold certificate that states the weight and purity of the medal. Gold assay cards make it easy to carry, show off, and store the items in which they are packaged, as many are the same size as a credit card. An intact gold assay certificate often makes selling the product on the secondary market much easier as assay certificate gold from trusted sources provides buyers with confidence that the product is as advertised.
What Are Gold Assay Marks?
Many items also have gold assay marks, also known as gold hallmarks. These markings are popular for things such as jewelry or antiques that do not otherwise have the backing of governments or security features that many other coins and bars do. The regulations concerning the appearance of gold hallmarks vary from country to country. These rules can include requiring the presence of the maker’s mark, which indicates who sent the item to an assay office, the assay office mark, which shows who certified the purity, and the karat measurement. The weight is not always marked on the item, as that can be measured at any time, including the time of sale.
In Conclusion
Gold assaying is a fascinating process for those who are intrigued by science. There are plenty of options available for private assaying. Still, marks, cards, and certificates from reputable assay offices make measuring the potential value of gold items far easier. While collectors do not need to understand all the science involved in gold assaying, having a fundamental understanding of what those measurements are and how to interpret them is essential for anyone who looks at the purchase and sale of gold as anything more than a hobby.
