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How does gold fineness differ from gold karat measurement?
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The Tanami gold mine, Northern Territory, Australia.
In the context of gold processing and jewelry, both karat and fineness are used to describe the purity of gold, but they utilize different mathematical scales to express that proportion.1
- Karat (K): This system measures gold purity based on a 24-part scale. One karat represents 1/24th of the total mass of an alloy, meaning pure gold is designated as 24 karats. For example, 18-karat gold contains 18 parts gold and 6 parts other metals, equating to 75 percent purity.213
- Fineness: This measurement expresses gold purity in parts per thousand. It provides a more granular representation of the metal's composition. For instance, gold with a purity of 99.9 percent is referred to as "three-nines fine," which corresponds to a fineness of 999.1
While the karat system is standard in the jewelry industry, fineness is a common way to denote the precise concentration of precious metals within an alloy.1