A karat stamp chart is used to determine gold’s purity. Many charts however, display the purity of other metals too. The following guide will make this clear.
Metal Purity Guide
.925 sterling silver is 92.5% pure fine silver. The common alloy is copper. 10k is 41.6% pure gold (10 parts out of 24). The common alloy is silver, zinc, copper, and nickel. 14k is 58.3% pure gold (14 parts out of 24).
The common alloys are the same as the 10k. 18k is 75% pure gold (18 parts out of 24). The common alloys are palladium (for white gold), nickel, copper and silver.
22k is 91.6% pure gold (22 parts out of 24). The common alloys are copper and silver. 24k is 100% pure gold.
900 Platinum is 90% pure platinum (900 parts out of 1,000). The common alloys are palladium, rhodium, ruthenium and other platinum group metals. 950 Platinum is 95% pure platinum (950 parts out of 1,000). Its common alloys are the same as that of 900 Platinum.
Karat and Carat
When studying karat stamp charts, you should not confuse the “karat” with the “carat”. The karat is used to refer to the purity of gold. The carat or ct, is the method used to determine the weight of gemstones.
For example, a diamond can weigh 1 carat, 2 carats etc. A gemstone weighing one carat is equal to 1/5 of a gram. This is equal to 0.20 grams. If a piece of jewelry is said to be 18k gold, it is 75 percent gold. Majority of the gold jewelries sold are 14k. To be considered solid gold, it must be at least 10k.
The karat is composed of 24 units. Pure gold is equivalent to 24 karats. 24k gold is known for its malleability. It can be shaped into hair-thin strands or paper-thin foil. While 24k gold is beautiful, it cannot be used as it is for jewelry.
For practical purposes, metals like zinc, copper, nickel and silver are included to produce a gold alloy. Copper and silver can be alloyed with gold. This can be done without affecting the color of gold. But if other metals are added, the color will change. For example, gold alloy will turn pinkish if copper is added.
A karat stamp chart is something you have to carefully assess before buying jewelry. By knowing how distinct it is from carat, mistakes can be avoided.