When buying or examining jewelry, oftentimes there are a lot of markings on the back of the pieces. To help you understand these important stamps or jewelry hallmarks– and understand which metals are fine, pure, and worth the higher price tag– we outlined the most frequently used hallmarks.

What is the difference between carat and karat?

To clarify two frequently used terms: a carat refers to the weight of a stone and is used to describe diamonds or gemstones. A carat equals 200 milligrams.

A karat, meanwhile, is a unit measuring the purity of gold. Gold jewelry is most commonly an alloy metal or a mixture of pure gold and a second, bonding metal. While 24 karat or 24K gold is pure gold, 18 karat gold is 18 parts gold, 6 parts alloy metal—or, differently said, 75% pure gold.

These numbers, especially karats, are important to understand when examining jewelry for authenticity and to recognize the specifications of your jewelry. On most quality jewelry, the specifications of your jewelry (like gold karat) will appear as a hallmark, or a stamp (or several) on the back or underside of the piece. Hallmarks connote the purity or fineness of the precious metals.

Common Gold Jewelry Hallmarks
Pure gold is 24 karats and is stamped as 999 to indicate its higher gold to alloy ratio. As we move down the scale of gold purity, 20 karat gold is stamped as 833 to represent the 20:24 (or .833) gold to alloy ratio. To simplify the other commonly used gold hallmarks, here is a handy chart of the caratage hallmarks and the gold purity they correspond to:

 

Common Platinum Jewelry Hallmarks
Just like gold, platinum is measured by its fineness. But, unlike gold, platinum is not measured in karats. Instead, it is measured by its purity percentage. The fineness hallmarks for platinum are as follows:

 

Common Silver Jewelry Hallmarks
While silver is pure, sterling silver is an alloy of pure silver and another metal. Therefore when it comes to silver hallmarks, silver is measured by its fineness and marked accordingly. One sterling silver hallmark of particular note is the 925 stamp used by Tiffany & Co.; if this 925 mark is not included on your alleged Tiffany & Co. jewelry, it’s an immediate indication the item is fake. Here is a breakdown of the other common silver hallmarks:

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