Whether you have inherited a piece that you just can't identify or want to be a more informed shopper, there are several pieces of information about gem identification here that may be useful to you. Many people simply trust that the person from whom they buy a gem is honest about the stone's attributes. While there are many reputable and trustworthy dealers out there, there also are some unscrupulous types looking to make a quick buck. As such, it is a good idea to get a handle on the basics of gem identification before you make a purchase.
Feel the stone. If it has a rough texture or seems delicate, it is not a gemstone. Gemstones are smooth and hard. Unless the stone you have is easily scratched or manipulated, you really cannot be sure that it is or is not a gem just by touch. To get an accurate assessment, you have to use a gemstone hardness testing kit. There are a wide range of kits available for purchase to suit both the amateur collector and the professional jeweler. Prices can range from less than $50 up to thousands of dollars. If you are only interested in testing one or two stones, you may want to have a jeweler do the test rather than invest in equipment.
Hold the stone up to the light. Examine it with a magnifying glass. Most gemstones have a flaw or two, but cut glass is flawless. Flaws, also called inclusions, detract from the value of a gemstone. However, don't assume that glass is more valuable just because it is flawless. Cut glass can be beautiful, but it doesn't have high value. Look for any spots or unevenness in the continuity of the stone's appearance. Some gems are flawless, but these are rare, very expensive and usually small. It is often difficult, even impossible to see every flaw without a loupe. Loupes are made specifically for jewelers and typically can magnify an item to 10 times its regular size. You can buy one for as little as $10, but really nice ones are closer to the $100 range. Whether you opt to examine the stone by yourself or get an expert opinion, realize that most people prefer a large stone with a flaw over a flawless, but small, stone.
Look for evidence that the stone has been altered. Stones can be dyed, heated or irradiated in an attempt to make them more attractive. Some stones are treated to fill in cracks. Others, like emeralds, may have been altered with the addition of a layer of synthetic gem. Not all alterations are a bad thing. Some heating techniques produce beautiful and valuable stones, such as the star ruby. Most other changes to a natural stone detract greatly from its value, durability, and in the case of irradiation, may even cause harm to humans. Cracks can never be properly fixed, and dyes can wear off. Alterations, especially in newer stones, are very hard for the amateur to detect. Stones that are older and altered with more primitive techniques can sometimes be spotted. Dye is often the easiest to spot because, with time, it discolors, cracks and flakes off the stone. Some alterations can be undone. Check with an expert before making a final decision on an altered stone.
Assess the presentation of the stone. Examine clasps on necklaces and bracelets. Check settings on rings and earrings. If the metal is cheap and flimsy, the stone is probably not valuable. Modern jewelry of good quality is set in platinum or gold that is at minimum 14 karats. Some valuable gemstones are set in sterling silver, but this is very rare and usually reserved for semi-precious stones. Antiques can be a bit trickier. Jewelry design is susceptible to trends just as much as any other fashion or decorative item. As such, jewelry from earlier periods may consist of very valuable stones set in a metal that is cheap looking by today's standards. Antique pieces have their own special charm and can be quite valuable even if the stones are not gems.
Research the color variations of a gemstone you hope to acquire. Many people don't know that sapphires can be colorless, diamonds can be yellow, garnets can be purple and topaz can be pink. Color is not the most salient factor in the classification of gemstones, but it can affect the value of the stone. Purple or green garnets, red or pink topaz and red diamonds are the most rare and valuable color variations. In any stone, the most valuable will have a vivid and pure color. The value of a certain shade will vary by gemstone. For example, medium-hued sapphires fetch higher prices than very pale ones.