The term karat describes the purity or percentage of gold in an object. In use since the late 1500′s, the karat is divided into segments of 24:

• Pure gold is 24/24, or 24 karat.
• 18 karat gold, also known as 750 gold, is 18/24 parts, or 75% gold.
• 14 karat gold, also seen stamped as as “585″, is 14/24 parts, or 58.5% gold.
• 10 karat gold is 10/24 parts gold, which is 41.7% gold. Jewelry or objects with less than 41.7% gold cannot legally be described as “gold” in the United States.

Where the jewelry is manufactured often dictates the karat chosen. In India, much of the jewelry is 22 karat gold. In Europe, 18 karat is the norm.

2 ounces of 24 karat gold casting grain

What makes up the rest of the item when it isn’t pure gold? That depends entirely on the desired result. White gold alloys for jewelry are often achieved by blending pure gold with nickel, zinc and copper or by blending pure gold with silver and palladium. Rose gold alloys are a mix of pure gold with mostly copper. A dark, rich yellow gold can be obtained by adding copper and zinc to pure gold.

There are plenty of proprietary alloys and special colors in the marketplace. Some alloys are better for casting; some are better for milling or hand fabrication. For the best quality, it is a requirement that the proper alloy mixture be matched to the manufacturing style and type of piece being created.