Here's what could be making up that golden tangle in your jewelry box:
Pure gold: When 100 percent of the metal is gold, it's called 24-carat gold, or 24k. That's the stuff worth almost $1,100 per ounce. But don't expect jewelry to be pure gold because that metal is too soft for a durable design. Virtually all gold gets mixed with other metals -- such as palladium, nickel, copper, silver, zinc, silicon and boron -- to increase its hardness. Mixing, however, dilutes the gold's value.
Solid gold: In the United States, a metal doesn't have to be pure gold to be called solid gold. Metals containing as little as 41.7 percent gold -- also known at 10-carat gold -- legally can be called solid gold.
14-carat gold: This is what most fine jewelry is made from, a mixture of 14 parts of gold and 10 parts of a base metal. Thus, a 14k-gold bracelet is just 58.3 percent gold. Some very fine jewelry is 18k gold (75 percent gold) and some is just 10k gold (41.7 percent gold). Many "class rings," for example, are 10k because that tends to be a stronger alloy and less expensive than rings made with a higher percentage of gold. U.S. jewelry that is 10k or higher usually will be marked with its carat quality, though marking is not required by law. Near the carat quality mark may be a U.S. registered trademark of the company that will stand behind the mark. The trademark may be in the form of a name, symbol or initials.
Gold-filled, gold overlay and and rolled gold plate: These are terms used to describe jewelry that has a layer of at least 10k gold mechanically bonded to a base metal. Jewelry marked gold- filled, gold overlay or rolled gold plate should include the karat quality of the gold used. Example: 14k gold overlay, 12k RGP or 1/20 12k GF. If the layer of gold is less than 1/20th of the total weight of the jewelry, any marking must state the actual percentage of carat gold, such as 1/40th 14k gold overlay.
Gold-plated: Jewelry can be thinly plated with gold in various ways, including mechanically plated or electroplated. Gold-plated jewelry has significantly less gold than gold-filled, gold overlay or rolled gold jewelry. Eventually, gold plating wears away, and how long that takes depends on the plate thickness. Gold electroplate has a layer at least 0.175 microns thick of 10k or more gold. Gold-flashed or gold-washed jewelry has an extremely thin plating of gold less than 0.175 microns thick.
-- J.N. Sbranti