These rich colors are the most appealing to the majority of people shopping for tanzanite. The two rings at the top of the image are examples. Tanzanite gems with a strong-to-vivid blue, purplish blue and violetish blue color are the most valuable. The four rings in the accompanying image contain tanzanite gems that range in color from a vivid blue at top left to a very light blue at lower right. Tanzanite occurs in a range of tones and color saturations that will appeal to almost any buyer who likes any of the other blue gems. Although they are all "blue" in color, each one is unique. The four blue faceted gemstones that are most often seen in commercial jewelry in the United States are aquamarine, topaz, sapphire, and tanzanite. This naturally blue, untreated tanzanite, is held in very high regard by some gemstone and jewelry buyers who seek it out when making a purchase. A small amount of tanzanite in the marketplace has a blue color that was produced naturally through the heat of metamorphism without any treatment by people. Today, nearly all of the gems being sold as "tanzanite" have a blue color that has been produced or enhanced by heating. Those gems can be heated to temperatures between 10 degrees Celsius and held at those temperatures for days or weeks. The heat treatment of tanzanite is very mild when compared to what is often done for gems such as rubies and sapphires. When vanadium-bearing zoisite is heated to a temperature of 600 degrees Celsius for about 30 minutes, the oxidation state of the vanadium is changed and that change causes or improves the blue color. The blue color of tanzanite is caused by small amounts of vanadium within the zoisite mineral structure. With those discoveries, there would be enough tanzanite to support a marketing effort that would introduce the gem to millions of people. They also determined that heating could convert some naturally brown or green zoisite into beautiful blue zoisite (tanzanite!). Soon after that discovery, laboratory experiments determined that heating could improve the color of some naturally blue stones. The discovery of transparent crystals of blue zoisite in the 1960s stimulated interest in the gem. Each of these minerals occurs in a wide range of other colors. The name " ruby" is used for red to slightly purplish red specimens of the mineral corundum the name " amethyst" is used for purple specimens of the mineral quartz and, the name " emerald" is used for green specimens of the mineral beryl. This type of color-variety name is not unusual. The name "tanzanite" is used for a color variety of zoisite that ranges from blue, through violet, to violetish purple. The mineral zoisite naturally occurs in a wide range of colors that include colorless, gray, yellow, brown, pink, green, blue, and violet. Because of its growing popularity, Tanzanite was designated as a modern birthstone for the month of December in 2002. This rapid rise to popularity was accomplished mainly by Tiffany's promotion and tanzanite's beautiful blue color. It is one of a very small number of gems of any color that have been discovered and brought to strong consumer popularity within the past century. In the short time since then, it has become the second most popular blue gem after sapphire. Table of ContentsĪlthough nearly all of the world’s most popular gemstones have been known and used for hundreds of years, tanzanite was not discovered in commercial quantities until the 1960s. "Tanzanite is the most beautiful blue stone to be discovered in 2000 years." - Tiffany & Co.
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