Gold is a metal that has several intriguing characteristics including its brilliant luster and its relatively easy ability to be shaped. These two qualities probably lead to its prolific use in jewelry throughout history. Currently, gold is used for all varieties of jewelry and it comes in a variety of different forms.
Because pure gold is far too malleable to sustain everyday use, gold is mixed with other metals to form an alloy. Depending on the proportions of other metal used, the finished gold has different qualities. Some of the other metals used in these alloys include silver, copper, zinc, and nickel. The relative amount of silver in the gold alloy determines the end color. For example white gold has a composition of 70% or more silver.
The gold content in gold alloy is measured in karats (K) (not to be confused with "carats" which are a unit of weight used in diamond grading.) Karats range from 1 to 24, with the higher numbers representing proportionally more gold content. Typically, the larger the number of Karats, the more valuable the gold is.
When purchasing a piece of gold jewelry you should be aware that the price will be determined not only by the karatage, but also by the quality of the craftsmanship and design of the piece. Every piece of jewelry should be stamped with the karatage (24K, 18K, 14K, etc.) It is illegal to sell anything less than 10K as gold in the United States.
Silver is an extremely shiny metal that can be polished to a higher sheen than platinum. Like most metals used for jewelry, silver is very malleable and durable. Silver is plentiful throughout the world and has played a major role in jewelry as far back as 4000 B.C.
Like gold, silver in its purest form is relatively soft. Thus it is often alloyed with other metals such as copper. When referring to the composition of silver (in parts of silver per thousand of alloy) the term "fineness" is used.
When purchasing a piece of silver jewelry you should be aware that silver of varying fineness can be sold. For example, Sterling silver is 92.5% silver and carries a fineness of 925.
Platinum is a very strong and heavy metal with a beautiful silver-white appearance. Because of its unique properties, it is one of the most durable precious metals used to make fine jewelry. Many people insist on using platinum for diamond settings because it does not add color to the appearance of the stone. Interestingly, platinum jewelry is also hypoallergenic as apposed to some gold alloys because of its purity.
Because platinum is more rare then gold, it is also more valuable. When purchasing a piece of platinum jewelry you should look for the marks that differentiate platinum from other metals such as silver or white gold. Platinum jewelry will be marked with 950Pt or Plat. In the United States this means that the piece must contain greater than 50% platinum.