A guided tour of Gemstones.....Aquamarine-Aquamarine has to live up to about the most inflexible color standards in the gem world. As a cousin of emerald in the beryl family of gemstones, aquamarine comes from a long line of elite colored stones. If you are in the market for top quality in one of these "sea-water" (Latin for aquamarine) blue gems, you will need the patience of Goldilocks. Too light or too dark just won't do, keep looking until you find one that's "just right." Deep clear sky-blue is the ultimate, and the intensity of hue must be uniform throughout the stone. Aquamarine under 10 carats will rarely measure up, as saturation of deep color is difficult to maintain in shallower stones.

The vast majority of aquamarine is mined in Brazil, with smaller, albeit typically better color, deposits found in Madagascar, Kenya, Zimbabwe, Nigeria and Zambia.

When mined, aquamarine is usually a bluish-green color. In order to achieve the deeper hue of aquamarine's standards, most stones are heat treated to remove the green tones. This treatment is permanent and fully accepted in the trade. The more intense the blue, the higher the price. Amethyst -As a member of the quartz family, amethyst is one of the most common, hence under-appreciated, gemstones on the market. Yet, its affordable beauty due to abundant availability also make amethyst extremely popular. A transparent rich lavender with flashes of red and pink at its finest, this birthstone for the month of February, and 6th wedding anniversary stone, will normally cost less than $100 per carat. Top quality specimens are found in Brazil and Zambia and will display an intense, deep-purple that is uniform throughout the stone. Color zoning and flaws that render a stone less than "eye-clean," greatly reduce value. It is estimated that over half of all amethyst on today's market is man-made, or a natural/man-made blend called "salted" amethyst. Amethyst can lose its color if heat treated, and care should be taken not to expose it to sudden temperature changes or overexposure to sunlight. Garnet -As long as you don't want blue, you can have garnet in any color you like. From the unique Mandarin orange of spessartine to the lush emerald green of demantoid, garnets are actually a lot more than one type of stone. Without getting too technical, here's a simple breakdown of the different types, colors and values of these beautiful gemstones.Rhodolite- Is a unique purplish variety, sometimes with the rich color of grape. Originally found in North Carolina, rhodolite garnet enjoys tremendous popularity in Japan, and can fetch an impressive $400 per carat. But, most specimens don't exhibit enough red to bring over $100. Peridot-The unique bottle-green of peridot has been treasured (even if Cleopatra thought they were emeralds) for almost 4,000 years. Originally mined solely on the Red Sea island of Saint John, Egypt, this birthstone for the month of August is now mostly produced in Arizona, Myanmar and Pakistan (source of the finest peridot ever seen.) Peridot is also the only gemstone on earth that has been found in meteorites!

A member of the olivine species, peridot, at its best, can be easily found for well under $300 per carat. This 16th wedding anniversary stone comes in a variety of shades from olive green to yellowish, brownish and a lively lime green. The purer the green, the higher the price. Typically, the presence of brownish tones will lower value. As opposed to the bright brilliance of emerald, top quality peridot green will have a more velvety or oily appearance. You should also consider clarity fairly closely when purchasing peridot. Make sure to examine the stones from the top, sides and bottom under various light sources. If you see black patches you should probably consider another stone. Topaz-There was a time, in the not too distant past, when all yellow and almost all green gemstones were called topaz. Perhaps this is why topaz isn't appreciated as it should be. Another reason it is considered common is that blue and green topaz is so readily available that it can cost as little as $20 per carat. But the golden-orange variety displays red and pink overtones it is called "Imperial Topaz" and can sell for over $2,000 per carat. Imperial topaz is also November's birthstone as well as the 23rd wedding anniversary stone. Lacking the reddish overtones, however, the lofty moniker, and value, is lost.

This doesn't mean that top-grade red and pink topaz is worthless. On the contrary, when fine specimens of these hues are found, they can cost as much as spinel of equal quality.

Most topaz is mined in Brazil and comes out of the ground in shades of light brown. It is then heat treated until it turns a lovely shade of pink. When natural red, orange and pink topaz is found (mostly in Pakistan) it can have lovely brilliance and clarity.

Opal-How do you determine the color of a gemstone that is known precisely for its multi-colored qualities? Opal is such a stone, and, consequently, several factors have been developed for that purpose. The important color signifiers for opal are: Type and body color. (Black is the most valuable type and body color.)

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