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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