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Jamming Gems Tourmaline Information
Tourmaline
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General Information:
The birthstone for the month of October, tourmaline is a stunning gemstone that
is found in more hues than any other gem. The name tourmaline comes from
"turmali," the Sinhalese (Sri Lanka) word for "more
colors." Ancient legend says that tourmaline is found in all colors
because it travelled along a rainbow, and along the way, gathered all the
color's of the rainbow. Over the centuries, people of royalty have adorned
themselves with this unique gemstone. Often times tourmaline will be bi or even
tri-colored. A tourmaline that is considered "watermelon," is green
on the outer edges, and pink in the center.
Tourmaline is found in several geological settings, most often in granite
pegmatites and their host rocks. This pegmatic tourmaline is generally black in
color. It is also found in eluvial and aluvial deposits, due to its relatively
high hardness and specific gravity. Tourmaline has also been found in
hydrothermal veins of quartz.
Tourmaline is a very complex aluminum borosilicate, there are eleven distinct
mineral species of tourmaline based on chemical composition: buergerite,
chromdravite, dravite, elbaite, feruvite, foitite, liddicoatite, olenite,
povondraite, schorl and uvite. The color seen in tourmaline is from the
presence of metal ions (Fe, Mn, Cr, V, Ti and Cu) in its crystal structure.
Indicolite is a common name given to blue tourmaline, and Rubellite for deep
pink-red tourmaline. The most expensive tourmalines are rich blue in color and
rubellite.
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Origin:
Tourmalines are mined in: Africa, Afghanistan, Australia, Brazil, Kenya,
Madagascar, Mozambique, Nigeria, Pakistan, Siberia, Sri Lanka, Tanzania, the
United States, and Zimbabwe. |
Common Treatments and Lab Created
Forms:
Heat treatment is sometimes used on tourmalines to lighten dark pieces or to
make white and pale pink tourmalines become a richer pink in color. When
lightened a dark gray or steel tourmaline will generally become minty green or
neon blue. |
Physical Properties:
Moh's Scale Hardness: 7-7.5
Specific Gravity: 2.96 - 3.31 (buergerite 3.31, dravite 3.03-3.15, elbaite
3.03-3.10, liddicoatite 3.02-3.08, schorl 3.10-3.25 and uvite 2.96-3.06)
Refractive Index: 1.610-1.735 (buergerite 1.655-1.735, dravite 1.610-1.661,
elbaite 1.615-1.655, liddicoatite 1.621-1.637, schorl 1.625-1.675 and uvite
1.612-1.638)
Fracture: conchoidal
Crystal system: hexagonal-rhombohedral
Colors: all colors
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