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විකිපීඩියා වෙතින්
Bi-colored tourmaline crystal, 0.8 අඟල් (2 cm) long
රසායනික සූත්‍රය(Ca,K,Na,[])(Al,Fe,Li,Mg,Mn)3(Al,Cr, Fe,V)6
පාට / පැහැයMost commonly black, but can range from brown, violet, green, pink, or in a dual-colored pink and green.
Crystal habitParallel and elongated. Acicular prisms, sometimes radiating. Massive. Scattered grains (in granite).
Crystal systemTrigonal
FractureUneven, small conchoidal, brittle
Mohs scale hardness7–7.5
LusterVitreous, sometimes resinous
Specific gravity3.06 (+.20 -.06)[1]
Polish lusterVitreous[1]
Optical propertiesDouble refractive, uniaxial negative[1]
Refractive indexnω=1.635–1.675, nε=1.610–1.650
Birefringence-0.018 to -0.040; typically about .020 but in dark stones it may reach .040[1]
Pleochroismtypically moderate to strong[1]
Red Tourmaline: Definite; dark red,light red
Green Tourmaline: Strong; dark green, yellow-green
Brown Tourmaline: Definite; dark brown, light brown
Blue Tourmaline: Strong; dark blue, light blue
Ultraviolet fluorescencepink stones—inert to very weak red to violet in long and short wave[1]
Absorption spectraa strong narrow band at 498 nm, and almost complete absorption of red down to 640nm in blue and green stones; red and pink stones show lines at 458 and 451nm as well as a broad band in the green spectrum[1]

  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.
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