Shades of gold

Whether the source is a fast-fashion emporium or a high-end retailer, most gold jewelry isn’t pure. It’s a mix of metals, the majority being untarnishable, noncorrosive, indestructible, $1,175-per-ounce gold.

And that mix determines color, which can be yellow, white, green, rose and red.

Twenty-four-karat gold — pure gold — is a reddish yellow, a hue that is unmistakably rich and bright. (And it’s generally considered to be too soft to be used in jewelry.)

Everything beyond that is a mix that yields different colors depending on the percentages of the metals melted together. An item made from 18-karat gold, for example, is 18 parts pure gold and 6 parts alloy, or 75% gold and a 25% alloy mix; 14-karat — the most common form of gold used in jewelry in the U.S. — is 14 parts pure gold and 10 parts alloy, or 58% pure gold.

The lower the karatage, or purity of the gold, the less yellow it will be. But precisely which shade is determined by the many types of metals that are added into the mix.

A white gold is made by adding white metals to gold, the most common being silver, platinum, palladium, zinc and nickel. Rose gold is made by adding copper; green gold, by adding copper with white metals.

“It’s simple color science,” said Duvall O’Steen of the World Gold Council. “It’s like Crayola art when you melt the colors together. When metals are heated, they become liquid and mix together, so the final result depends on the ingredients.”