Precious Metals: The Foundation of Fine Jewelry
Not all metals are created equal. Jewelry metals fall into two categories: base metals (copper, zinc, tin, nickel, lead, iron) and precious metals (gold, platinum, silver, and palladium). Precious metals earn that designation through their allure, rarity, workability, and durability.
Gold
Gold’s appeal comes from its color, luster, resistance to corrosion, and the simple fact that people have been drawn to it for millennia. Pure gold (24K) is too soft for most jewelry, so it’s alloyed with other metals to increase tensile strength and hardness. Gold is 19 times as dense as water — you can feel the heft in your hand.
The karat system measures gold purity: 24K is 99.99% pure, 18K is 75%, 14K is 58.3%, and 10K is 41.7%. In the US, 14K is the most popular jewelry alloy — a practical balance of durability, color, and cost.
Gold alloy colors depend on what metals are mixed in. Yellow gold (14K and 18K) combines gold with copper, silver, and zinc. Rose gold increases the copper ratio. Green gold increases the silver. White gold uses nickel or palladium with copper and zinc, and is often rhodium-plated for a brighter white finish.
Platinum
Platinum is highly resistant to tarnish, takes a beautiful polish, and is harder to scratch than gold or silver. It rates 900 or 950 fineness (90–95% pure) and is often alloyed with iridium, ruthenium, cobalt, or copper for additional hardness. It can also be rhodium-plated for a whiter finish. Platinum has what metallurgists call “metal memory” — superior holding power that makes it tend to return toward its original shape. That’s why it’s a preferred metal for securing valuable stones.
Silver
Sterling silver is 92.5% silver (925 fineness) with 7.5% copper — the minimum purity to legally carry the “silver” designation in the US. It’s about half as dense as gold, bright white with excellent workability. The trade-off: sulfur in the air reacts with silver to form silver sulfide (tarnish). Vermeil (silver gilt) is a thin coating of gold over silver, at least 2.5 microns thick.
Palladium
A relative newcomer in the jewelry world, palladium is similar to platinum but less dense. It offers a naturally white color without plating, making it an increasingly popular choice.
