Gemstones that display multiple colors are rare and unusual. Some gems display different colors under changing lighting conditions, and are known as color change gems. Others will display different colors when viewed from different angles. These gems are known as diachroic (two colors) or pleochroic (more than 2 colors). This phenomenon derives from the double refraction of light.
But some special gems will display multiple colors under the same viewing conditions. These bicolor and multicolor gems often have regions or zones of different colors. Tourmaline especially is noted for this property, though it can also be found in other varieties, such as Ametrine and Fluorite.
Tourmaline (like Sapphire, Spinel, Beryl and Quartz) is colorless when pure. It is the presence of small quantities of one or more coloring agents than give these gems their distinctive colors. Gems with this property are known as allochromatic. It is typically trace elements with atomic numbers in the range of 22 to 29 that cause the distinctive colors: titanium, vanadium, chromium, manganese, iron, cobalt, nickel, and copper.
Tourmaline seems to be particularly susceptible to absorbing trace elements during its formation. Pink Tourmaline, resulting from the presence of manganese; and Green Tourmaline, resulting from iron, are the most common.
Some Tourmalines provide a visual record of their crystal growth by displaying two or more areas of different color. These are known as bi-color or tri-color Tourmalines. Most often they feature a combinations of pink and green or some variation. The color range is quite wide, ranging from orange to purple to brownish-pink and blue-green to apple-green. High quality specimens are valued by collectors and make unique and beautiful jewelry.
Bi-color Tourmalines are found in most of the tourmaline deposits in the world, including Brazil, Nigeria, Madagascar, Afghanistan and the USA (California and Maine).
Notable Gems from the AJS Collection
This month we feature a range of fine Bi-Color Tourmalines from Mozambique and Nigeria. Click on any gem photo for details.
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A stunning large Bi-color Tourmaline from Mozambique, 30 mm in length! This fine Tourmaline is 70 percent bright yellowish green and 30 percent blue-green. A clean, bright and perfectly cut stone that will make an amazing pendant. Guaranteed natural and untreated.
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A lovely large Bi-Color Tourmaline from Nigeria, with gradients of green, red and gold. This is perfectly clean material which has been expertly cut and polished to perfection. This is a superb gem Tourmaline for your collection. Guaranteed natural and untreated.
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A vivid Bi-color tourmaline from Mozambique. A beautiful color combination, this is a really gorgeous gem with intense reddish pink and light orangy pink hues. Guaranteed natural and untreated.
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A splendid Bi-Color Tourmaline from Nigeria with gradients of orange, bronze and green. This is perfectly clean material which has been expertly cut and polished to perfection. Just a gorgeous gem Tourmaline for your collection. Guaranteed natural and untreated.
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A high quality Bi-Color Tourmaline with unusual and unique icy colors. This is completely clean material with excellent cutting, at an excellent price. Guaranteed natural and untreated.
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A very nice Bi-color Tourmaline with deilcate shadings of pink and gold. Completely clean, this excellent material has been expertly cut with a fine polish. Guaranteed natural and untreated.
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News from AJS and the Gems World
Summer Sale!
20% Off on All Gems with Payment by Bank Transfer
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Offer expires August 31
Ask the Gem Experts
Each month we answer questions from our customers. We welcome your questions and you can submit a question from our contact page.
How important is origin to the value of a gemstone?
It is always interesting to know where a gemstone came from, and sometimes we are able to state the specific mine as well as the country of origin. But origin alone is no guarantee of value.
Famous mines are highly regarded because they have a history of producing high quality gems. The mines in Mogok in Burma, for example, have produced many valuable pigeon-blood Rubies over centuries. But recent finds in Madagascar and Mozambique have also produced some outstanding Rubies. So it's wise to evaluate the specific gem instead of buying based on origin.
Some gemstone varieties were named for their origin -- Paraiba Tourmaline (Paraiba region of Brazil), Tanzanite (Tanzania), Danburite (Danbury, Connecticut), Brazilianite (Brazil) and Mali Garnet (Mali). But these varieties may also be found in other locales. When neon blue-green Tourmaline similiar to the Brazilian material was found in Mozambique, the gem trade agreed to use "paraiba" as a variety name rather than an origin. Most of the Danburite in today's market comes from Mexico, and Connecticut hasn't been productive for years. But thus far Tanzanite has only been found in Tanzania.
