All gold is colored of course—we can all picture stacks of gold bricks in some mythical vault: a rich, lustrous golden hue reflecting a bright glint of light that meets the eye with a ubiquitous bling. But not all gold is the pure gold of those iconic bricks.
Since pure 24 carat gold is usually too soft to be used in jewelry, most of the gold we see on a daily basis is an alloy, or a mixture of gold with other metals. And while many of the metals used to strengthen gold are specifically chosen to preserve the color we all know and love, some alloy metals can produce different colors.
White gold is a mixture of gold and a white metal (most commonly nickel, palladium, or manganese), and it is available in a wide variety of hues, from pale yellow to tinted brown to pale rose-red. Often covered with a plating of rhodium for durability, white gold is probably the most popular ‘colored’ gold. It is commonly used in all kinds of jewelry, from rings and necklaces to pins and brooches.
The qualities of white gold vary depending on the metals used, with nickel producing a hard alloy suitable for pins and rings, and silver and palladium yielding a more malleable alloy, good for gemstone settings. Typical alloys used for making jewelry can include as much as 10% nickel, which can lead to allergic reactions for some, especially on rings when the rhodium plating grows thin.
Also known as pink or red gold, rose gold is a gold and copper alloy, and its ‘redness’ is directly related to the copper content in the alloy—the more copper, the stronger the red color. Typical alloys are 75% gold, with the remaining 25% being copper (red gold) or copper and silver (rose and pink gold). Red gold was extremely popular in Russia in the early 1800s, and is recently experiencing a comeback in the 21st century, being commonly used for engagement rings and wedding bands.
Green gold is an alloy of silver and gold, once known in its naturally occurring state as “electrum.” The color of green gold is subtle—more a ‘yellow gold with a greenish tint’—and is best highlighted against areas of yellow, white, or rose gold. Traditional green gold was made of 75% gold and 25% silver, though harder metals like nickel and zinc are now commonly added for strength. Cadmium can also be used to produce green alloys, but health concerns have greatly curtailed its use.
Intermetallic Compounds and Plating
Purple and blue gold result from intermetallic compounding rather than alloying, and their properties can be quite different from gold. Purple gold (or amethyst gold) is a gold-aluminum intermetallic, and though nearly 80% gold, it is extremely brittle, and is often cast and faceted to be used as a “pseudo-gem” in jewelry.
Blue gold is an intermetallic compound of gold and indium, typically used only to surface plate gold or silver to attain a blue color. Black gold can be achieved by electroplating with black rhodium, or by patination using sulfur and oxygen compounds. These so-called ‘exotic’ gold colors remain rare, and are mainly used as highlights in multi-colored gold pieces.
Diamond Estate Jewelry Buyers purchases all colors of previously-owned gold jewelry set with high-quality gemstones and diamonds. If you are looking to sell your gold jewelry, please contact us today for a free verbal appraisal and immediate cash offer.