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name:
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Green Tourmaline
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| gemstone variety:
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Tourmaline
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| trade name 1:
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Green Tourmaline
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| trade name 2:
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Verdelite
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| trade name 3:
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| basic colour:
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green
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Colour :
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all shades of green from pale yellowish-green to a
strong bluish-green
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Quality :
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the more desirable colour is a blue-green rather than
an olive or black green colour. The intensity should be an
optimum not a maximum. Facetted green Tourmalines should
have no visible inclusions and balanced proportions in the
cut.
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History :
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The name tourmaline is derived from the Singhalese
word "turamali" meaning gemstone. Verdelite is a composed
word from the Latin word "verde" =green and the Greek word
"lithos"=stone. Dutch sailors which brought tourmalines from
Ceylon to Europe in the 17th century, called them
"aschntrekkers" because they attracted ashes and could be
used to clean pipes. The reason is the physical property to
change its electrical charge when heated, and to become a
polarised crystalline magnet which attracts light objects.
Today we have fine colours of green to bluish green
Tourmaline from Brazil and Africa.
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Curiosities / Saga :
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|
Countrys of Origin :
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Brazil, Nigeria, Namibia, Tanzania, Mozambique,
Madagascar, Afghanistan, China, USA (California)
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Birthstone :
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October - Tourmaline
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Hardness :
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7.5
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Treatment :
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sometimes heat-treated
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Size :
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normally from 0.50 to 10.00 carats, fine green
Tourmalines above 20.00 carats are rare
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Specific gravity :
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3.10 - 3.26
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Chemical Composition Formula :
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Na(Li,Al,Fe)3 Al6 (BO3)3 Si6O18 (OH)3F
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Chemical Composition Name :
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Hydrous and fluor bearing sodium- lithium- aluminium-
iron- boronsilicate
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Crystal system :
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trigonal
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Light refraction :
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1.610 - 1.640
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Double refraction :
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0.016 - 0.022
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