Gold is one of the most valuable and precious metals in the world. It is present in bodies of water and the earth's crust. Trace amounts are even present in plants and animals. It is, however, difficult and expensive to extract. In modern mining operations approximately 3 tons of ore are needed to  extract one ounce of gold. The many desirable qualities found in gold, along with its scarcity, have made it the most popular metal for use in jewelry today. Because gold can come in so many forms, there is a grading system designed to alert the goldsmith and the buyer how valuable the item is, and what it is made of. Because pure gold is extremely soft, other metals are mixed with the gold to make the piece more durable, less expensive, and to alter it’s color.

Gold jewelry never goes out of style, and for good reason, because gold is as wearer-friendly as it is beautiful. Pure gold doesn't react with other elements to create tarnish, the residue that accumulates on some metals before transferring to your skin as a stain. Sometimes people have allergy or staining problems with metals that are combined with gold, but the gold itself is rarely a problem.

Gold can be worked into nearly any shape, from tiny strands that do not break easily to very thin sheets. One ounce of gold can even be hammered into an ultra thin sheet that's ten feet square. Gold can be manipulated nearly any way the artisan desires.

Pure gold is so soft it is rarely used in jewelry. Jewelers deal with various gold alloys, collectively called karat gold (also spelled 'carat'). For gold, karat grade is used to express the proportion of gold in an alloy or the quality of a gold alloy. Karat (K) tells the number of parts, by weight, of gold in 24 parts of alloy. The higher the percentage of pure gold, the higher the karat. Fine gold (pure) is 24 karat. The proportions in other karat grades are listed in the table below. All jewelry is required by law to be stamped so consumers will know the quality of gold used. Jewelry made in North America is typically marked with the karat grade (10K, 14K, etc.), and jewelry made in Italy is typically marked with the "fineness" such as (417, 583, etc.). So if your jewelry does not have a karat grade stamped on it, check for a 3-digit fineness number.

With the popularity of white metal jewelry, it is important to understand that all gold starts out yellow. White gold is yellow gold that has been alloyed with nickel or palladium (both white metals) to make the yellow gold turn white. Neither one of these alloys makes yellow gold turn completely white and mirror shiny like. The nickel-gold alloy still appears slightly yellow, and the palladium-gold alloy a little gray. This is why almost all white gold jewelry is rhodium-plated. Rhodium is is in the same metal group as platinum - it is very bright and very hard.

Rose gold is also known as pink gold or even red gold, and is a mixture of pure yellow gold with a high percentage of copper. It has a very subtle and delicate color that may intensify somewhat with age due to a slight, but commonly regarded as attractive, tarnishing of the copper alloy. Rose gold is created by increasing the copper-colored alloys mixed with the gold, and decreasing the silver-colored alloys. 14K rose gold contains as much pure gold as 14K yellow gold but, because of the increased copper, is slightly pinker in color.

Adding other metals to the mix also allows a metallurgist to change the color of gold. Palladium or nickel can be added to create white gold. Adding copper produces a rose or pink tint, while silver gives gold a greenish cast. When metals are added to the gold the result is an alloy, a blended mixture of the metals. Solid gold is a term that can be used to describe an item that's at least 10K (in the US) gold all the way through. Even though it's a gold alloy--18K, 14K, or anything down to 10K--it can be called solid gold.

There are Federal Trade Commission rules that require all jewelry items sold in the United States as gold tobe described by "a correct designation of the karat fineness of the alloy." No jewelry item less than 10K may be sold in the United States as gold jewelry. 9K gold jewelry is popular in Europe.