How to Identify Precious Metals
Gold can usually be identified by markings on your jewelry in karats, such as: 8kt, 9kt, 10kt, 14kt, 18kt, 22kt or 24kt. Some gold may be marked as .585 for 14kt and .750 for 18kt.
What is a Karat Gold? Karat denotes the amount of gold by weight in an alloy, known as the fineness. One karat is 1/24th gold purity by weight, therefore pure or fine gold is known as 24 karat. The popular jewelry alloys in the U.S.A. are:
22 karat or 22/24ths by weight of gold (91.67% pure gold) marked as 22K or 22kt
18 karat or 18/24ths by weight of gold (75.00% pure gold) marked as 18K or 18kt
14 karat or 14/24ths by weight of gold (58.53% pure gold) marked as 14K or 14kt
10 karat or 10/24ths by weight of gold (41.67% pure gold) marked as 10K or 10kt
10 karat is the minimum recognized purity of an alloy to be called "gold" in the United States.
Gold Markings and Color: In the United States, the purity of gold is designated by Karat markings. Pure gold is 24K and is too soft for making jewelry. Alloying elements like copper, silver, nickel and zinc are added to strengthen it. The karat and color of gold are determined by the amount of those elements that are added. For example, If you divide 10K by 24K, you would have 41.67% of pure gold and the other elements would be 58.33% of copper, silver, and zinc for yellow gold. For pink (rose) gold, a larger percentage of copper is used. For white gold, a larger percentage of nickel is used. Yellow and white are the most common colors for gold, but gold can also be green and rose-colored.
Platinum / Palladium: Both platinum and palladium are part of the platinum precious metals groups. These are also considered to be precious metals, based on their rarity. Both are considered hard precious metals, so they are usually only alloyed 5-10%. Both metals are also naturally white in appearance.
Platinum: For an object to be called platinum it must contain at least 95% pure platinum. So if your jewelry has the words platinum, plat or pt then it contains a minimum of 95% pure platinum. Alloys containing less than 95% pure platinum but 85% pure platinum or above will be marked with the parts per thousand number as follows:
900Plat or 900Pt (contains 90% pure platinum)
850Plat or 850Pt (contains 85% pure platinum)
So if your jewelry is marked plat it will contain a minimum of 95% pure platinum. If it is marked 900Plat it will contain a minimum of 90% pure platinum. If it is marked 750Plat, it will contain 75% pure platinum, regardless of any other marks present.
Palladium: There is no actual hallmarking laws regarding palladium in the U.S. at present, but jewelers will mark palladium jewelry in much the same way as platinum, except using the marks pall or Pd instead of plat or Pt.
Silver:For an object to be marked as either solid silver or sterling silver, at least 92.5% of the objects total weight must be fine silver. The usual marks used are sterling or 925. In some cases objects may be marked ster or STR.
Coin silver is 90% pure silver.
Vermeil is gold plated on sterling silver and will be valued as silver.