Source: Afghanistan, Africa, Brazil, Madagascar, Mozambique, Namibia, Nigeria, Sri Lanka, Tanzania, USA (California, Maine), Zambia
Birthstone: October (Alternate: Opal)
The name "Tourmaline" (Tourmalin German, Turmalina Spanish, Tormalina Italian) is derived from the Sinhalese (Sri Lanka) word "Tura Mali", meaning "stone of mixed colors." Tourmaline appears in many colors, including clear, pink, yellow, blue, red, green and black. Ancient Egyptian legend explained the array of colors in tourmaline this way: On it's long journey from the middle of the earth up toward the sun, the tourmaline traveled along a rainbow collecting all the colors of the rainbow. This is why tourmaline came to be known as "the rainbow gemstone." Tourmaline owes its rainbow coloration to trace impurities such as chromium (red), iron (dark blue, dark brown), lithium (green, pink), manganese (pink), schorl (black) and vanadium (green).
Tourmaline has a hardness of 7 to 7 1/2 on the Mohs scale. The Toughness of Tourmaline is Fair to Good and exposure to thermal shock should be avoided. Tourmaline belongs to the Trigonal crystal system with a Parallel and Elongated Striated Crystal habit. Elongated Tourmaline crystals are asymmetrically terminated (hemimorphism). Some varieties of tourmaline will display dichroic qualities. Tourmaline has a refractive index of 1.624.
Tourmaline is a complex crystalline silicate (cyclosilicate) containing aluminum, boron and other trace elements. Tourmaline is piezoelectric which means that heating, rubbing or pressurizing the crystal gives it an electric charge It also is pleochroic, which makes it appear darker from some angles than from others. Tourmaline's pyroelectric quality was discovered in the early seventeenth century.
Chemical composition: Na(Mg,Fe,Mn,Li,Al)3Al6(BO3)Si6O18(OH,F)4
Some of the finest Tourmaline in the world is found in igneous rock pegmatite dikes and alluvial deposits or cascalho, located in the area around Virgem da Lapa in Minas Gerais, Brazil. Rivers have washed through these deposits scattering stones throughout this region. Some of the mines that have produced the greatest specimens of gem crystal tourmaline and aquamarine are the primary deposits of Araçuaí, Corrego do Urucum, Cruzeiro, Golconda, Jonas, Limoeiro, Medina, Pedra Azul and Xanda. Primary deposits in Afghanistan, and alluvial deposits in Sri Lanka (Ceylon), Nigeria and Namibia are also primary sources.
Tourmaline Color Classification
Each color of tourmaline is given its own name. Tourmaline colors are categorized as: "Anchorite" (colorless), "Cat's Eye" (pink and green), "Chrome" (dark green), "Dravite" (brown), "Elbaite" (green), "Indicolite" (blue), "Paraiba" or "Neon" (vibrant blue, green), "Pink", "Rubellite" (deep red), "Schorl" (black), and "Watermelon Tourmaline" or "Bi-Color" and "Tri-Color Tourmaline" (usually green transition to red). Rubellite tourmaline has an appearance that is similar to ruby.
Watermelon Tourmaline
Watermelon tourmaline (above, right) is known for its concentric bands of color featuring a reddish, pink, purple, or magenta center surrounded by a whitish zone enclosed in a olivine green "rind" area. Watermelon tourmaline is typically found in Brazil.
Pink Tourmaline
A principle source of Pink Tourmaline can be found in Afghanistan. Afghan tourmaline can be found among metamorphic pegmatite veins of gneiss, mica schist, and quartzite located in in the Panshir Valley, north-east of the capital city of Kabul.
Paraíba Tourmaline
For information on cuprian elbaite, go to: Paraíba
Further Reference on Tourmaline:
The Mineralogical Record - A Mineral Collector's Knowledge Database
Color in Cuprian Elbaite
American Mineralogist - The Origins of Color in Minerals
