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TANZANITE, CHROME DIOPSIDE AND IOLITE

TANZANITE

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Tanzanite is a beautiful gem. In addition to its beauty, it has some properties that require it to be given special care. Tanzanite is best suited for earrings, pendants and other jewelry items that will not encounter abrasion and impact. It is less suited for use in a ring. Many jewelers recommend that "tanzanite rings are for dress rather than daily wear"

Tanzanite is a trade name that was first used by Tiffany and Company for gem-quality specimens of the mineral 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 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 blue to bluish purple to bluish violet specimens. This type of 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

The discovery of transparent crystals of blue zoisite 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 zoisite into beautiful blue zoisite. With those discoveries there was enough blue zoisite to support a marketing effort that would introduce the gem to millions of people. Today, nearly all of the gems being sold as "tanzanite" have a blue color that has been produced or enhanced by heating in a laboratory. 

The blue color of tanzanite is caused by small amounts of vanadium within the zoisite mineral structure. When the mineral is heated to a temperature that is high enough to change the oxidation state of vanadium, the color of the gem is changed. This color transition occurs at a temperature of about 600 degrees centigrade.

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. The four rings in the image in the right column of this page contain tanzanite gems that range in color from a vivid blue at top left to a very light blue at lower right. 

Tanzanite gems with a strong to vivid blue, purplish-blue and violetish-blue color are the most valuable. The two rings at the top of the image at right are examples. These rich colors are the most appealing to the majority of people shopping for tanzanite. 

Tanzanite and sapphire are the two favorite blue stones in the gem marketplace. Tanzanite is a gem that many people desire because of its unique beauty and characteristics. Others purchase tanzanite because it has a beauty similar to sapphire but at a much lower price. 

Tanzanite also competes with lab-created sapphires that are lower in price than natural sapphires. In that comparison, some buyers will select tanzanite because they would rather have a stone that was created by nature instead of one created in a lab. 

Most tanzanite has a light to medium tone and low to medium saturation. The tanzanite rings at the bottom of the image at right are examples. Although these gems are not considered to be top color, many people prefer them and gladly pay the lower price. Tanzanite in these softer colors often appeals to buyers who like aquamarine and blue topaz. 

Tanzanite stands out in mall and chain store jewelry displays because most stones have a distinct hint of purple or violet in their color. People who have experience looking at gems and pay attention to color will quickly notice tanzanite in a display case of blue gems. 

CHROME DIOPSIDE

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Chrome Diopside is a chromium-rich, transparent to translucent variety of gemstone-quality calcium magnesium silicate. It is one of the rarer varieties of diopside and belongs to the pyroxene family of minerals. Diopside is most famous for its attractive forest-green color, but depending on the impurities and coloring agents, diopside gemstones can actually occur in a variety of different colors, including common black to near-black, rare violet-blue and light yellowish-green to medium dark-green. Chrome diopside is an officially recognized variety of diopside and one of the newest gems on the market today. Even though it's considered relatively new, it very quickly made its way into the mainstream gem trade and became one of the most popular green gemstones of today. Despite the widespread belief that green gemstones are common, naturally occurring green gemstones are actually quite rare.

With chrome diopside, it is common for color to steadily darken as the size of the stone increases. In many cases, larger stones can be so dark that they can appear to be near black. Unfortunately, in order to achieve the most desirable color, this typically results in faceted stones being under 2 carats in weight. Any faceted stone over 2 carats with a rich medium-dark green color is considered to be very rare. Most diopside occurs very opaque with very little or no gemstone value, but on rare occasion, some opaque, black to near-black materials may exhibit chatoyancy or asterism, which is considered rare and valuable. These are known in the trade as cat's eye diopside and star diopside, respectively.

As a lesser-known gemstone, diopside hasn't gained much fame as of yet. In ancient times, some people believed green diopside had fallen from the tree of life and therefore the dead should be buried with a diopside to ensure renewal of life. In some cultures green diopside was associated with peace and tranquility and put on the forehead before rest, in order to ensure sweet dreams. Chrome diopside is believed to protect from all evil and bad memories.

The name 'diopside' was derived from the Greek words 'di' and 'opsis', meaning meaning 'two' and 'vision'. Due to the origin of its name, diopside has earned a reputation for being a visualization stone, which is thought to increase creative vision, as well as awareness. It is thought to be able to improve intellect, most particularly mathematical, analytical and statistical ability. In addition, chrome diopside can alleviate aggression and stubbornness, while enhancing the emotions of love and commitment. Physically, chrome diopside is believed to aid with the healing of a few chronic diseases and disorders, including heart, lung and circulatory system problems. Chrome diopside is a stone for Pisces and although it is not an official birthstone for any month, it is still associated with the month of March as anastral gemstone.

IOLITE

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Iolite is the gem-quality blue or blue-violet variety of cordierite. While iolite enjoyed popularity in jewelry in 18th-century Europe, this naturally beautiful gemstone is relatively new to the jewelry market and is regaining popularity with the public. Because of its hardness and pleochroism, iolite is one of the most difficult stones to cut. It must be cut in a certain direction to take advantage of the best color, which can be tough when the shape of the rough doesn't lend itself to cutting in that same direction.

Iolite should not be cleaned in ultrasonic or steam cleaners. It is safe to clean iolite with warm soapy water, but avoid abrupt changes in temperature. Iolite is typically light to dark blue or violet-blue, but it may also occur in light shades of yellow, green, gray, or brown. Violet-blue iolite is considered ideal color. Iolite is strongly trichroic, meaning that it shows three colors when viewed from different angles. A cube-shaped piece of iolite can appear blue from one angle, clear from another, and surprisingly golden from another.

Most colored stones are valued first and foremost on the intensity and saturation of their color. Iolite is no exception, but there is a caveat. Like blue sapphire, there's a narrow range of tones in which iolite's rich blue displays at its best. Otherwise, iolite's purplish-blue hues can cross the line into "inky" territory, making the stone overdark and lifeless or, in the worst cases, appear black.