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| Tourmaline fact file | |
| Crystal Structure: long and sub-triangular Chemical Composition: silicate of Boron and Aluminum Hardness: 7-7.5 MOHS | Refractive Index: 1.620 and 1.640 Colors: black, red, pink, green, and blue “Watermelon” colors – red inside and green outside |
Opal and Tourmaline are the birthstones of October. Opal was originally the gem trade’s recognized birthstone for October but in 1952 pink tourmaline was added as an alternate stone to opal.
Although the original designation for tourmaline was pink tourmaline, the practice has become that many people accept tourmaline of any color for October’s birthstone. Tourmaline comes in nearly every shade one can find on a color chart or color wheel—therefore, tourmaline has become a popular stone in recent years. Tourmaline may show a couple of different phenomena: watermelon tourmaline and particolor tourmaline. In the former, the outer layer of the crystal is green and the inner part of the crystal is red and there may be small black inclusions that resemble black seeds similar to a cross section of watermelon. The distinction is now used for any tourmaline that has an outer layer of the crystal with one color and an interior of another. These color variations may be brought about by varying concentrations of metallic cations that that were favored in crystallization of tourmaline from a solution or melt. In the past names such as rubellite and indicolite were used for red and blue tourmaline respectively. Since the mineral suffix ite implies each are a different mineral, it is now preferable to use the
terms red tourmaline and blue tourmaline, etc.
Chemical composition
Tourmaline is a complex silicate of Boron and Aluminum. Many different elements are able to find a spot for substitution in the crystal lattice and this accounts for all of the different colors of tourmaline that are available to the gem fancier. Finished stones have a soft luster and the two refractive indexes, 1.620 and 1.640
allow for some doubling of back facets and inclusions in the stone. Tourmaline may also show some long tubes that are oriented parallel to the c-axis of the crystal. Tourmalines are piezoelectric which means they can generate electrical charges when heated, compressed, or vibrated. Because of these charges, tourmalines attract dust and small materials.
Colors
Iron tourmaline (schorl) is black and has the least value. Elbaite is the gemstone tourmaline that features an abundance of colors such as red, pink, green, and blue. Dichroic tourmalines appear to be two different colors when viewed from different angles. “Watermelon” tourmalines have red on the inside and green on the outside
due to their concentric crystal composition.
Buying Tips for Tourmaline – October Birthstone Jewelry
Tourmaline’s many color variations make it an example for a kind of wrong labeling. For example, one will sometimes see the usage of names such as Brazilian sapphire or Brazilian emerald for blue and green tourmaline respectively. Such names confuse the potential buyer into thinking the stone is something other than what it really is.Prices range from $50 to $1,000 per carat, for an average-to-good-quality one-carat stone.
Caring Tips
Warm soapy water and a soft brush is your best bet for cleaning this october birthstone. Do not use mechanical cleaners.
Where Found
Tourmaline is found near silica-rich rocks and granite. In the United States tourmaline has been found in Maine, North Carolina, and California. Brazil has produced many fine tourmaline crystals of many colors that have found use both as cut gems and as museum specimens. Namibia, Nigeria and Zambia in Africa have produced some fine gem tourmaline in recent years. Tourmaline deposits have been found in Sri Lanka, Afghanistan, Myanmar, Tanzania, Zimbabwe, Namibia, Brazil, Madagascar, and the United States (California, Maine, and Connecticut).
History, mythology
Wearing pink tourmaline is said to attract love and green ones will attract success.