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Schorl Tourmaline
(repeatin unit)
(Ca,K,Na,[])(Al,Fe,Li,Mg,Mn)3(Al,Cr, Fe,V)6
Creestal seestemTrigonal
ColourMaist commonly black, but can range frae broun, violet, green, pink, or in a dual-colored pink an green.
Creestal habitParallel an elongatit. Acicular prisms, whiles radiatin. Massive. Scattered grains (in granite).
FracturUneven, smaa conchoidal, brickle
Mohs scale haurdness7–7.5
SkinkleVitreous, whiles resinous
Speceefic gravity3.06 (+.20 -.06)[1]
Polish skinkleVitreous[1]
Optical propertiesDouble refractive, uniaxial negative[1]
Refractive indexnω=1.635–1.675, nε=1.610–1.650
Birefringence-0.018 to -0.040; teepically about .020 but in dark stones it may reak .040[1]
Pleochroismteepically moderate tae strang[1]
Reid Tourmaline: Definite; dark reid,licht reid
Green Tourmaline: Strang; dark green, yellae-green
Broun Tourmaline: Definite; dark broun, licht broun
Blue Tourmaline: Strang; dark blae, licht blae
Ultraviolet fluorescencepink stanes—inert tae vera waik reid tae violet in lang an short wave[1]
Absorption spectraa strang narra band at 498 nm, an naur complete absorption o reid doun tae 640nm in blae an green stanes; reid an pink stanes shaw lines at 458 an 451nm as weel as a braid band in the green spectrum[1]

Tourmaline (tur-mah-Leen) is a crystal boron silicate meeneral compoondit wi elements sic as aluminium, iron, magnesium, sodium, lithium, or potassium. Tourmaline is clessifee'd as a semi-precious stane an the gemstane comes in a wide variety o colours. The name comes frae the Sinhalese wird "Thuramali" (තුරමලි) or "Thoramalli" (තෝරමල්ලි), which applee'd tae different gemstanes foond in Sri Lanka.

References[eedit | eedit soorce]

  1. a b c d e f g h i Gemological Institute of America, GIA Gem Reference Guide 1995, ISBN 0-87311-019-6
  2. Mindat tourmaline group Accessed September 12, 2005. This website details specifically and clearly how the complicated chemical formula is structured.