No, it’s not a fly (as in “What’s that in my soup?). It’s the reason that your gold is the color it is. Many years ago, when your grandparents and great-grandparents were buying jewelry, gold followed the Henry Ford school of thought – you could have gold any color you wanted it, as long as it was yellow. As time and technology progressed, metallurgists (that’s people who work with metals) learned that you could make gold different colored by adding other elements to pure gold.
At its most basic level, pure gold which is known as 24 Karat gold, is a distinctive yellow color. The problem in working with pure gold, however, is that gold is the most malleable, or pliable of all the metals. One ounce of pure gold can be made into a sheet of 300 square feet! While that is an asset in making jewelry, it’s a liability if you want to keep it looking like jewelry. Jewelry makers needed to make gold sturdier, and to do that, they added other metals to the pure gold. Copper, silver, and zinc were added to the pure yellow gold to strengthen it. These additional metals also changed the appearance of the gold. Its distinct yellow color was softened by the additional metals. The new combination of metals is called alloys.
Since the alloy is no longer pure gold, it can’t be called 24 Karat gold. The Karat quality of the metal is based on the percentage of pure gold in the alloy. The most common Karat qualities sold in the United States are 10 Karat, 14 Karat, and 18 Karat gold. The percentage of pure gold in each of these alloys is 41.8% in 10 Karat gold (10 divided by 24), 58.5% in 14 Karat gold (14 divided by 24), and 75% in 18 Karat gold (18 divided by 24). The remaining percentage of the other metals is dependent on who is doing to alloying of the gold and is usually kept secret so that no two alloys are exactly the same.
Now that you know about yellow gold, let’s talk about the other colors of gold that are found in most jewelry today. The most common alternative to yellow gold is white gold. Because gold is naturally yellow in color, metals that are white have to be added in order to make white gold. The predominant metal that is added to yellow gold to make it white is nickel. Other metals that are added include copper and zinc, but those are added primarily to add strength to the gold as with yellow gold. White gold follows the same Karat qualities as yellow and the other colors of gold.
Another color of gold found in jewelry is known by many names. We generally lump them all together and call it rose gold. Rose gold also goes by the names pink gold, red gold, and strawberry gold. The color of rose gold is most distinctive, and is caused by the predominant addition of copper (think copper pennies) to the gold. Silver and zinc are also added for strength.
Less commonly used today is green gold. Green gold gets its greenish tinge by the predominant addition of silver to pure gold. Copper and zinc are still added to the alloy.
In recent years, two colors of gold have made their presence known in fashion jewelry – black gold and brown gold, also known as chocolate gold. These colors are created not so much from the alloying of pure gold, but of the molecular processing of gold. Black gold can be created three ways – 1) by electroplating of regular Karat gold with black Rhodium, 2) by the controlled oxidation of gold alloyed with cobalt or chromium, 3) adding carbon to the metal and processing the alloy using with a method called Chemical Vaporization and Deposition. Similarly, chocolate gold is created by the same process starting with rose gold. In both of these alloys, the process permanently alters the surface of the metal and it can only be removed by scraping off the outer layers.
Two other colors of gold can be created using alloying of pure gold, but both are impractical for use in jewelry production due to the brittleness of the alloy. Purple gold is created by adding aluminum to pure gold. Blue gold is created by adding indium to pure gold. Both of these alloys are over 75% pure gold, so both alloys are considered 18 Karat in quality.
Gold alloys come in a palette of colors, but yellow and white represent nearly all jewelry being produced today. Rose gold is making its presence known, but the other colors will usually be found only by working with a custom jeweler. To each their own as to their color preference, but whatever you choose, you can be assured it will be beautiful and to your liking.