Pure gold is a very soft and pliable metal. The extreme malleability, ductility, and softness of pure gold makes it practically useless for jewelry applications. Jewelry made of pure gold would easily bend and distort in the course of normal wear. To get around this problem, jewelers use an alloyed form known as karat gold (not to be mistaken with metric carat used to measure diamond weight). Alloying increases gold's hardness and provides a variety of different colors. White gold contains about 10 - 20 % nickel, plus zinc, copper, platinum, and palladium. These alloys make white gold a harder metal than yellow gold. Gold content is specified by the codes 14k, 18k, etc. The K (karat) number specifies how many parts, by weight, of pure gold is contained in 24 parts of the alloy. Thus:
10k = 10/24 = 41.67% pure gold
14k = 14/24 = 58.33% pure gold
18k = 18/24 = 75.00% pure gold
And of course, 24k means 100% pure (or fine) gold. Gold itself is impervious to tarnishing and requires very strong and dangerous chemicals for it to dissolve.
Platinum is regarded as the preeminent metal for fine jewelry. It is rarer and thus more expensive than gold. The white luster of platinum is unique. It is also the strongest precious metal used in jewelry, and is almost twice as heavy as 14k gold. This weight is one of platinum's strongest selling points, because it gives "heft" to fine jewelry, which people naturally equate with value. Platinum has rapidly grown in popularity in recent years, becoming the new choice for many diamond engagement rings because the luster of platinum is said to bring out the brilliance of diamonds better than gold. Platinum in jewelry is actually an alloyed group of six heavy metals, including platinum, palladium, rhodium, ruthenium, iridium and osmium. These other metals are so similar to platinum in weight and chemistry that most were not even distinguished from each other until early in the nineteenth century. Today it is often alloyed with copper and titanium. It is the only precious metal used in fine jewelry that is 90% to 95% pure, largely hypoallergenic and tarnish-resistant. Platinum jewelry is marked 900Pt, 950 Plat, or Plat.
Gold and platinum are durable, sturdy and dependable, and make ideal settings for your precious diamond jewelry. However, to get a lifetime of enjoyment from your jewelry, be sure to keep it clean and safe.