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Diamond Testers Explained

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Almost everyone who has walked into fine jewellery stores has at least seen a device that is used to test diamonds. This device is not really used for analyzing color or quality; it is used to identify the gemstone as genuine.

The most commonly used diamond testers are based upon thermal conductivity technology. The technology measures the ability of a material to transfer heat. Most of the testers on the market have a copper tipped probe which is pressed up against a flat surface of the gemstone to be tested. In most cases the flat surface of the faceted gemstone is often the table. The tester then analyzes the loss of heat from the tip.

Diamond is one natural crystal which exhibits the characteristic of thermal conductivity. No other natural gemstones can match its ability to conduct heat. Based upon this, the idea of the thermal conductive tester was born. This type of diamond identification was well accepted and widely used in the 1980's by jewellers and appraisers as it proved to work well. There were some slight drawbacks to the testers, as there usually are with all kinds of tools. To obtain good readings, the tip of the probe had to be placed firmly upon the gemstone. If the tip touched any metal a false indication would be given. The tip must be held firmly into position for a few seconds to obtain a good reading. Melee stones set into pave mountings were often slightly more time consuming to test than larger stones set with prongs. Even with these little nuances the thermal conductive diamond testers were the tool of choice on the market.

During the 1990's a new synthetic stone entered the jewellery market under the name of moissanite. The chemical structure is basically silicon carbide which exhibits some of the same characteristic properties as a diamond, even thermal conductivity. Suddenly the best tools on the market for quick and accurate testing drops down a notch. Now there is not just one method to accurately identify diamonds; two methods must be applied. Today the thermal conductive diamond testers are now also equipped with the ability to measure reflectivity to aid in identification of a real diamond vs. moissanite.

Like all tools the diamond thermal conductive tester must be used in an appropriate fashion as described by the manufacturer. Compliance with the manufacturers instructions are usually carefully maintained to avoid results of diamond materials obtaining non-diamond results. That is to say, the thermal conductive tester historically errs on the negative side if there is any doubt.

But there are occasions that it does err on the positive result side incorrectly too! The tester errs on the positive side when it hits metal and other heat conducting materials. Many people posed the question of when does it provide positive results when other non diamond gemstone material is applied. That question has been answered thanks to rough diamond swindlers overseas. They brought one important thing into the limelight and that is the environment you are conducting your testing in. The external environment that the test is being conducted in or the environment that the stone is stored in can make a difference to the results of the test also. So extreme care has to be taken when using diamond testers to get absolutely accurate test results!


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