Fine jewelry that is chosen with care can be a good investment and last for generations as well. Before you shop for jewelry, it is important to know as much as possible about what you are buying. Gemstones, such as diamonds, emeralds, rubies and sapphires are minerals that are considered attractive and valuable because of their color, shine or rarity. But there are no universally accepted standards for grading diamonds or other gemstones -so it is important to deal with a jeweler you can trust when buying or having stones appraised. Diamonds are the hardest and most brilliant of gemstones. Their value is determined by what are known as the 'four c's': Color, clarity, cut and carat. Diamonds have little color, although some very rare diamonds have traces of blue. A good diamond will have a pure, clean, colorless transparency. Clarity refers to internal marks and surface blemishes. Those with fewer and less noticeable marks are rarer, and likewise more expensive. Properly cut, a diamond catches all the light that enters the top, breaks it into all the colors of the spectrum and reflects it back through the top of the stone. Diamonds that are cut to ideal proportions are more expensive than those that are not. Finally, carat refers to the weight of the stone. Keep in mind that since large diamonds are much rarer than small ones, the larger the stone the greater the price per carat. There are a number of diamond 'look-alikes' on the market, one is called cubic zirconia, sometimes called 'c-z diamonds'. These are not real diamonds, so don't let the name mislead you. When shopping for gold, be aware that pure gold is 24 karat. Here, karat refers to parts of gold and not weight. In its pure state, gold is too soft for jewelry and so it's combined with other metals. The most common alloy in the United States is 14 karat gold, which is 14 parts gold and 10 parts of another metal. Other popular combinations include 10 karat and 18 karat. Silver is also too soft to be used by itself. Sterling silver contains 92 and one-half percent silver and seven and a half percent copper. Silver plate could contain a layer of silver as thin as one 100-thousandth of an inch.