By Adrianne Jerrett
Updated Aug 30, 2022

Chris Collins/The Image Bank/GettyImages

Gold has fascinated humans for millennia, from the green‑gold coins of ancient Lydia to the vibrant jewelry of the 14th‑century Chimu Empire. In today’s market, the numbers you see on a piece—10, 14, 18, or 24—are not arbitrary; they are industry‑standard indicators of the metal’s purity.

Carat, Karat, or Carrot? Clarifying the Terms

The words carat and karat often get mixed up. A carat (abbreviated ct) historically measured both the weight of gemstones and the purity of gold. The term karat (abbreviated K) was later adopted exclusively to denote gold purity. In many English‑speaking countries, you’ll see 10K or 14K used on jewelry to signify the gold content. While carat can also refer to gemstone weight, in most contexts it’s the karat that tells you how pure the gold really is.

What Is an Alloy?

Pure gold is notoriously soft, which limits its use in everyday wear. To enhance durability, strength, color, and cost, gold is blended with other metals—creating an alloy. Common alloying elements include silver, copper, nickel, zinc, and platinum. Silver, for example, resists tarnish and helps keep gold bright and scratch‑free.

Alloy composition also affects hypoallergenic properties. Gold alloys that contain higher levels of nickel or cadmium can trigger skin reactions. If you have metal sensitivities, opt for high‑karat gold (18K or higher) or gold/silver blends, which tend to be allergen‑free.

How Is Gold Purity Measured?

Gold purity follows a parts‑system standard. Pure gold is technically 99.9% gold with 0.1% other metals, but the industry rounds it to a 24‑part scale: 24K equals 100% gold. Therefore:

• 18K (18K) = 18 of 24 parts gold = 75% gold, 25% alloy.
• 14K (14K) = 14 of 24 parts gold = 58.3% gold, 41.7% alloy.
• 10K (10K) = 10 of 24 parts gold = 41.7% gold, 58.3% alloy.

In many countries, 10K is the lowest grade that can still be marketed as “gold.”

The Many Colors of Gold

Gold’s hue is dictated by the alloying metals:

• Yellow gold – the classic blend of silver, copper, and zinc.
• Rose or red gold – high copper content gives it a warm pink tone.
• White gold – often mixed with palladium or nickel to mimic platinum’s silvery look.
• Specialty colors like blue, purple, and black gold result from adding iron, aluminum, or cobalt, respectively.

The value of each color varies with market demand and the cost of the alloying metals. For instance, 18K rose gold is usually more affordable than 18K yellow or white gold because copper is less expensive than silver or platinum.

Why Knowing These Details Matters

When you’re shopping for jewelry, understanding carats, alloys, and color nuances empowers you to make informed choices that align with your style, budget, and skin sensitivities. Armed with this knowledge, you can confidently select pieces that truly reflect the quality and character you desire.