COLORED GOLD JEWELRY - Composition of Gold Alloys in Colored Gold Jewelry - The purity or fineness of gold in the jewelry is indicated by its karat number -- 24 karat (24K or 24 kt) gold is as pure as gold for jewelry gets. Gold will form alloys with most metals, but for jewelry, the most common alloying metals are silver, copper, and zinc. Other metals may be added, especially to make colored gold.

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Colored Gold Jewelry

Composition of Gold Alloys in Colored Gold Jewelry

by Anne Marie Helmenstine, Ph.D. 

When you buy gold jewelry, it isn't pure gold. Your gold is really an alloy, or mixture of metals.

The purity or fineness of gold in the jewelry is indicated by its karat number -- 24 karat (24K or 24 kt) gold is as pure as gold for jewelry gets.

Gold that is 24K is also called fine gold and it is greater than 99.7% pure gold. 

Proof gold is even finer, with over 99.95% purity, but it is only used for standardization purposes and is not available for jewelry.

So, what are the metals that are alloyed with gold?

Gold will form alloys with most metals, but for jewelry, the most common alloying metals are silver, copper, and zinc.

However, other metals may be added, especially to make colored gold.

Here's a table of the compositions of some common gold alloys:

Gold Alloys 

Color of Gold	Alloy Composition
Yellow Gold (22K)	Gold 91.67% Silver 5% Copper 2% Zinc 1.33%
Red Gold (18K)	Gold 75% Copper 25%
Rose Gold (18K)	Gold 75% Copper 22.25% Silver 2.75%
Pink Gold (18K)	Gold 75% Copper 20% Silver 5%
White Gold (18K)	Gold 75% Platinum or Palladium 25%
White Gold (18K)	Gold 75% Palladium 10% Nickel 10% Zinc 5%
Gray-White Gold (18K)	Gold 75% Iron 17% Copper 8%
Soft Green Gold (18K)	Gold 75% Silver 25%
Light Green Gold (18K)	Gold 75% Copper 23% Cadmium 2%
Green Gold (18K)	Gold 75% Silver 20% Copper 5%
Deep Green Gold (18K)	Gold 75% Silver 15% Copper 6% Cadmium 4%
Blue-White or Blue Gold (18K)	Gold 75% Iron 25%
Purple Gold	Gold 80% Aluminum 20%

Anne Marie Helmenstine, Ph.D.

Ph.D. in biomedical sciences from the University of Tennessee at Knoxville - Oak Ridge National Laboratory.

Science educator with experience teaching chemistry, biology, astronomy, and physics at the high school, college, and graduate levels.

ThoughtCo and About Education chemistry expert since 2001.

Widely-published graphic artist, responsible for printable periodic tables and other illustrations used in science.

Experience

Anne Helmenstine, Ph.D. has covered chemistry for ThoughtCo and About Education since 2001, and other sciences since 2013. She taught chemistry, biology, astronomy, and physics at the high school, college, and graduate levels. She has worked as a research scientist and also abstracting and indexing diverse scientific literature for the Department of Energy.

In addition to her work as a science writer, Dr. Helmenstine currently serves as a scientific consultant, specializing in problems requiring an interdisciplinary approach. Previously, she worked as a research scientist and college professor. 

Education

Dr. Helmenstine holds a Ph.D. in biomedical sciences from the University of Tennessee at Knoxville and a B.A. in physics and mathematics with a minor in chemistry from Hastings College. In her doctoral work, Dr. Helmenstine developed ultra-sensitive chemical detection and medical diagnostic tests.

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https://www.thoughtco.com/composition-of-gold-alloys-608016