Understanding Gem Jewelry

Tanzanite, a relative newcomer to the market, may lack in rich gem legend and lore, but it has rapidly won the public's favor since its discovery some 30 years ago.

No recent gemstone discovery has had more of an impact on the world gemstone market than tanzanite. Portuguese prospector Manuel d'Souza discovered this gem in Tanzania in 1967 while searching for sapphire. Tanzanite was named after its country of origin by Henry Platt, vice president of Tiffany & Co. in New York, one of the world's most influential jewelers who began an aggressive marketing campaign to introduce tanzanite to the public in the 1980s.

Tanzanite's mass appeal lies in its great color, a mixture of two gem favorites: sapphire and amethyst. Popular for its rich violet blue to purple tones, tanzanite has tonal depth comparable to sapphire. Rarely found in a pure blue, tanzanite almost always displays purple overtones. It is highly tri-chroic; that is, it shows varying amounts of blue and violet in incandescent light and daylight. In small sizes, tanzanite tends toward the lighter tones (lavender is most common). Tanzanite crystals naturally occur in various colors: yellow, golden brown green and blue (but rarely).

Tanzanite is a velvety-blue to purple variety of the mineral zoisite, a silicate of calcium and aluminum. Prior to its discovery, the only variety of zoisite used for gems was a pink-colored gem known as thulite. A green variety of zoisite was recently discovered which is called chrome (or green) tanzanite, owing its color to chromium.

On the Mohs scale of hardness, tanzanite ranks 6-7. This gem is considered relatively soft and thought should be given when designing jewelry to protecting the stone from harsh wear. Although its dispersion is low at 0.019, tanzanite has a moderate luster. Large stones up to 50 carats are available however, the larger the gem the more saturated the color. Limited quantities of natural gem-quality tanzanite are found almost exclusively in Arusha, Tanzania.

Warm soapy water and a soft brush is your best bet to clean tanzanite. Do not use an ultrasonic or steam cleaner. Avoid contact with acids and sudden temperature changes (as may occur in some jewelry repair and design work). It is important to buy fine tanzanite from a reputable retailer who will provide, in writing, all pertinent information regarding the gem including enhancements and special care notes.

Although it is not a birthstone, tanzanite is a recommended gift for couples celebrating their 24th wedding anniversary, according to contemporary jewelers' anniversary gemstone lists. A noted 122.7-carat faceted tanzanite is on display at the Smithsonian Institution

Gemstone colors

Emerald - The greenest of the green, emeralds were cherished by the Romans above all other gems. Find out what makes this favorite of Cleopatra's so unique

Garnet - January's birthstone is famous for being as red as a ruby, but this colorful gem actually comes in every color but blue. Discover this elusive chameleon

Opal - Opals are the gem world's silvery mirrors, reflecting back every color in a flash of pastels or a streak of fire. Uncover this enchanting stone.

Peridot - Peridot is a gem that gets around. From ancient Egypt to present-day Apache mesas, even in space meteorites--you never know where its green gleam is going to show up.

Ruby - The color of courage and blood, rubies are even more precious per carat than diamonds. See why the Biblical authors to modern collectors use them as the measure of ultimate value.

Tanzanite- Millions of years in the making, deep-violet tanzanite revealed itself to humans only thirty years ago. Read about this newest discovery.

Sapphire - Blue as the perfect sky, sapphires have been used as protective talismans for centuries. Learn about the versatility of this stone that combines hardness and color variation like no other.

Tourmaline - Available in every color and saturation, this tough crystal has become a popular substitute for rubies, emeralds, and sapphires. Unmask this clever chameleon.

Turquoise - The lovely opaque blue of turquoise is produced by traces of copper in the stone. Elements of iron will also create a pretty, pronounced green hue. Oxides contribute to the stone's famous gray, brown or black veining.