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The Colors of Gold

Pure gold is recognized by its bright yellow color and luster, traditionally considered attractive in the jewelry industry: more importantly for the jewelry designer, it maintains these characteristic properties essentially forever, as this metal does not oxidize in air or water. However, gold does readily create alloys with many other metals; such alloys have modified metallurgical properties, and most important for the jewelry designer, different and exotic colors.

Common colored gold alloys such as rose gold can be created by the addition of various amounts of copper and silver (see diagram below, taken from Wikipedia Commons). The popular white gold is an alloy containing palladium or nickel (although because the latter is toxic, its release is tightly controlled by legislation in a number of countries). Less common is the addition of manganese, aluminum, iron or indium, as well as other elements, which produces more unusual colors of gold.

Pure (24k) gold is an extremely soft metal—ancient ornaments were likely created by early man picking the gold up off the ground and simply pounding it with a rock or other implement. Today, however, it is usually alloyed with base metals for use in jewelry, to change its hardness and ductility, melting point, color and other properties. Alloys with lower caratage, typically 22k, 18k, 14k or 10k, contain higher percentages of copper or other base metals, silver or palladium. Copper is the most commonly used base metal, yielding a redder color: 18k gold which is one-quarter copper can be found in antique and Russian jewelry; this metal has a distinct, though not dominant, copper cast, and is termed rose gold; 14k gold-copper alloy is nearly identical in color to some bronze alloys. Blue gold is produced by combining iron and purple gold, but is generally only used for very special applications as this gold alloy is quite brittle and difficult to work with when making jewelry. Fourteen and 18k gold alloys with only silver are greenish-yellow and referred to as green gold. A white 18k gold alloy containing 17.3% nickel, 5.5% zinc and 2.2% copper is silvery in appearance. Due to nickel's toxicity however, alternative white gold alloys are available based on palladium, silver and other white metals, but they are more expensive due in large part to the palladium, which is more costly than nickel. High-carat white gold alloys are far more resistant to corrosion than are either pure silver or sterling silver. In a highly unusual and novel use of gold's variety of colors, the Japanese craft of Mokume-gane exploits color contrasts between laminated colored gold alloys to produce decorative wood-grain effects (see article on Mokume-gane).