Värde tanzaniter
By Joel E. Arem, Ph.D., FGA, Barbara Smigel, PhD. GG, International Gem Society.
The Definitive Guide to Tanzanite Gemstone: Everything You Need to Know
Tanzanite has had a rapid rise to prominence among jewelers and gem enthusiasts. Although naturally reddish brown, this transparent zoisite variety achieves a stable, beautiful blue to violet color with heat treatments. Home » Gemstones » Tanzanite.
Faceted blue tanzanite: This violetish blue tanzanite is an exceptional faceted oval weighing 8. It is easy to see why Tiffany's called tanzanite "the most beautiful blue stone to be discovered in years. Photo copyright by Tanzanite Direct and used here with permission. Tanzanite is a trade name that was first used by Tiffany and Company for gem-quality specimens of a mineral named zoisite with a blue color.
Tiffany could have sold the material under the mineralogical name of "blue zoisite," but they thought the name "tanzanite" would stimulate customer interest and be easier to market. The name "tanzanite" was given because the world's only known tanzanite deposit of commercial importance is in northern Tanzania. The mines are all located in an area of about eight square miles in the Merelani Hills, near the base of Mount Kilimanjaro and the city of Arusha.
In the short time since then, it has become the second most popular blue gem after sapphire. 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. This rapid rise to popularity was accomplished mainly by Tiffany's promotion and tanzanite's beautiful blue color. Because of its growing popularity, Tanzanite was designated as a modern birthstone for the month of December in Natural blue tanzanite: The pair of crystals shown on the left is the same pair of crystals shown on the right.
They have different apparent colors because tanzanite is pleochroic - it appears to be different colors when viewed from different directions. If we cut a faceted stone from the crystal pair on the right and oriented the cutting so that, in this view, we were looking down onto the top of the table, the stone would have a blue face-up color. If we did the same with the crystal pair on the left, the stone would have a purple face-up color.
If the table of the stone were tilted slightly in any direction, an intermediate face-up color would be produced. This pair of crystals has not been heated by humans. Their colors are natural. It is an example of tanzanite having spectacular natural color. The mineral zoisite naturally occurs in a wide range of colors that include colorless, gray, yellow, brown, pink, green, blue, and violet. The name "tanzanite" is used for a color variety of zoisite that ranges from blue, through violet, to violetish purple.
This type of color-variety name is not unusual. 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. Each of these minerals occurs in a wide range of other colors. The discovery of transparent crystals of blue zoisite in the s stimulated interest in the gem.
Soon after that discovery, laboratory experiments determined that heating could improve the color of some naturally blue stones. They also determined that heating could convert some naturally brown or green zoisite into beautiful blue zoisite tanzanite! With those discoveries, there would be enough tanzanite to support a marketing effort that would introduce the gem to millions of people. The blue color of tanzanite is caused by small amounts of vanadium within the zoisite mineral structure.
When vanadium-bearing zoisite is heated to a temperature of degrees Celsius for about 30 minutes, the oxidation state of the vanadium is changed and that change causes or improves the blue color. The heat treatment of tanzanite is very mild when compared to what is often done for gems such as rubies and sapphires. Those gems can be heated to temperatures between and degrees Celsius and held at those temperatures for days or weeks.
Today, nearly all of the gems being sold as "tanzanite" have a blue color that has been produced or enhanced by heating. 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. 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.
Tanzanite colors: The tanzanite gems in these rings show a range of blue color that can be found in tanzanite. Most buyers prefer stones with a strong-to-vivid blue color like the ones in the top row of this image. These stones sell for a much higher price than stones with a lighter color. However, many people prefer the lighter-color gems and gladly pay their lower price. Tanzanite has a range of blue colors that place it in competition with sapphire, blue topaz, and aquamarine.
The Value Of Tanzanite In 2024 By Color (A Luxurious Gem!)
Tanzanite occurs in a wide range of tones and saturations that compete well with sapphire, blue topaz, and aquamarine. The four blue faceted gemstones that are most often seen in commercial jewelry in the United States are aquamarine , topaz , sapphire , and tanzanite. Although they are all "blue" in color, each one is unique. 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.