GOLD ALLOYS. Because 24 karat, pure gold (24/24 = 100% gold) is very soft, wears away very rapidly with ordinary use, and is considerably more expensive than harder gold alloys; it is rarely used for making gold jewelry. 22 karat gold (22/24 = 91.7% gold) is also of poor durability and is therefore also less suitable for making gold jewelry than harder alloys. To be legally marketed in the United States as gold, gold jewelry must be at least 10 karat.
Popular alloys that offer increased strength (hardness) and extended wear ability are 18k (18/24 = 75.0%), 14 karat gold jewelry (14/24 = 58.3%), and 10k (10/24 = 41.7%), with such designations usually being stamped on the clasp or inside edge or rim of the gold jewelry item. Gold jewelry items may also be stamped .999 (24k), .917 (22k), .750 (18k), .583 (14k), or .417 (10k) as another way of indicating their karat rating fineness (common in Europe). Though it is relatively unusual today, older items may be stamped "p" or plumb (e.g. 14kp), indicating that they are exactly the 24k, 22k, 18k, 14k, or 10 karat designation.
Price Comparisons, everything else being directly comparable (e.g. link shape, mm or gauge size, gram weight, length, and manufacturing process) 18k gold will be approximately 30% more expensive than 14k gold jewelry and 80% more expensive than 10k gold; and 14k gold jewelry will be approximately 40% more expensive than 10k gold.
Multi-colored gold (yellow, white, pink, green, etc.) is produced by combining different percentages of alloy metals (primarily copper, silver, nickel, and zinc) with gold, but still retains its full 18, 10, or 14 karat gold rating.
Gram Weight. 24k, 22k, 18k, 14k, or 10k gold is weighed in grams and troy ounces (31.1 grams), and though it is becoming more popular, it is still relatively unusual for retail merchants to sell gold jewelry by the gram. While the karat fineness is always well marked, the Client is often left in the dark as to the gold jewelry item's weight, making an informed decision as to the value offered nearly impossible. As a general rule, if the merchant can't or won't state the gram weight of a jewelry piece or mounting, purchasers should exercise greater caution when buying from that merchant.
American Ounces (Avoirdupois) vs. Troy Ounces. Troy weight is a system of units of mass customarily used for precious metals, gemstones, and black powder. It is commonly confused with the avoirdupois system commonly used in the United States for most applications of trade like in grocery stores or the post office. A troy ounce is equivalent to 31.1 grams as opposed to the avoirdupois ounce which is 28.3 grams. When spot gold or gold futures are quoted on a financial exchange, they are always quoted in troy ounces.