What Does the Au 750 Gold Stamp Mean on Jewelry?

Jewelry often features various markings indicating important characteristics. Among these, “Au 750” is a common stamp found on gold pieces. Understanding this mark provides insight into the gold’s composition and quality, helping consumers make informed decisions.

The Meaning of Au 750

The “Au” in “Au 750” is the internationally recognized chemical symbol for gold, derived from the Latin word “aurum.” This symbol is universally used in metallurgy and jewelry to denote the presence of gold. Its inclusion in the stamp identifies the primary metal of the item.

The number “750” in the marking indicates the gold’s purity level in parts per thousand. This means that 750 out of every 1,000 parts of the metal alloy are pure gold, translating directly to 75% pure gold by weight. This system of marking purity in parts per thousand is a global standard.

This 75% purity level directly corresponds to 18 Karat (18K) gold. The karat system measures gold purity on a scale of 24 parts, where 24 Karat (24K) represents 100% pure gold. Therefore, 18 parts out of 24 equals 75% pure gold. The “Au 750” stamp, along with “18K” or “18ct,” serves as a clear indication of the gold’s significant purity.

Alloy Components and Physical Qualities

The remaining 25% of the metal in Au 750 gold is composed of various other metals, known as alloys. These alloying metals are intentionally added to pure gold to enhance its properties. Common alloying metals include copper, silver, zinc, palladium, and sometimes nickel, each contributing unique characteristics.

Pure gold is naturally very soft and malleable, making it unsuitable for durable jewelry that withstands daily wear. The addition of these alloys increases the gold’s hardness, strength, and durability. This makes 18K gold more resistant to scratches, dents, and general wear and tear compared to higher purity gold like 24K.

Different combinations of alloying metals also influence the final color of the gold. Copper, for instance, is primarily responsible for the warm, reddish hue of rose gold. White gold often achieves its appearance through the addition of white metals like palladium or silver, and it may also be rhodium-plated for a brighter, whiter finish. Yellow gold typically uses silver and copper in specific ratios to maintain its traditional golden color while increasing its strength.

Recognizing and Caring for Au 750 Gold

Identifying Au 750 gold involves looking for specific hallmarks or stamps on the jewelry. These marks are usually small and discreetly placed, often found on the inside of rings, on the clasps of necklaces or bracelets, or on the back of pendants and watch cases. Common markings include “750,” “18K,” or “18ct,” all signifying 75% gold purity.

These hallmarks are often applied by manufacturers or, in some regions, by independent assay offices that verify the metal’s purity. An assay office mark provides additional assurance regarding the gold’s authenticity and stated fineness. Checking for these stamps is the most direct way to confirm a piece’s gold content.

Proper care for Au 750 gold jewelry helps maintain its beauty and longevity. Regular cleaning with mild soap and warm water, using a soft brush to gently remove dirt, is recommended. After cleaning, rinse the jewelry thoroughly and dry it with a soft, lint-free cloth. Avoid exposing gold jewelry to harsh chemicals, such as chlorine bleach or strong cleaning agents, as these can damage the metal and any gemstones. Storing Au 750 gold pieces separately in a fabric-lined jewelry box or soft pouch can prevent scratches and tangles.