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A microalloy is a gold alloy which has very tiny amounts of other elements added to it to change its physical properties. The elements selected must be able to alter the microstructure of the gold and yet be non-toxic and stable during jewelry manufacturing to allow the production of fine jewelry. Both of these requirements are met in PureGold. High karat gold microalloys were first introduced to manufacturing jewelers in 1996. In order to meet hallmarking requirements for 24K jewelry, a microalloy must be at least 0.997 gold by weight. PureGold easily meets this requirement with a purity of 0.9985 gold. PureGold also has the greatest hardness of any 24K microalloy available worldwide that meets this 24K requirement. PureGold can have a hardness of 180 Vickers, equivalent to the hardness of some 18K golds. Since the microalloy is 0.9985 fineness (99.85%) gold, its density is nearly equal to that of 99.99% gold, 19.3 g/cc. This high density and a melting point of 1073.9 degrees Celsius makes working with PureGold significantly different from 14K or 18K gold. The table below gives some of the physical properties of PureGold. |
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The “as cast” product has a hardness of 96 Vickers indicating it can be used in the lost wax process in suitable designs. Age hardening brings the hardness to 110 V. Designs that work well in platinum will also work well in PureGold. Following casting, pieces can be age hardened (250 degrees Celsius for three hours) to increase the hardness. |
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For more details on casting PureGold, see the Casting
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A hardness of 110 Vickers in a cast piece that has been
age hardened is typical. The grain size in cast pieces is sufficiently
small to ensure a strong product and a fine finish. The grain
in a cast ring shank is shown at left.