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[plee-ok-roh-iz-uh m] /pliˈɒk roʊˌɪz əm/
the property of certain crystals of exhibiting different colors when viewed from different directions under transmitted light.
Compare dichroism (def 1), trichroism.
1855-60; pleochro(ic) + -ism Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for pleochroism
  • Both are light colored, and the pleochroism of the hypersthene is sometimes quite faint.
  • The mineral is a low-grade metamorphic amphibole characterized by pleochroism in shades of blue and violet.
  • In addition to color, a grain should be checked for pleochroism using polarized light.
British Dictionary definitions for pleochroism


a property of certain crystals of absorbing light to an extent that depends on the orientation of the electric vector of the light with respect to the optic axes of the crystal. The effect occurs in uniaxial crystals (dichroism) and esp in biaxial crystals (trichroism)
Derived Forms
pleochroic (ˌpliːəˈkrəʊɪk) adjective
Word Origin
C19: pleo- + -chroism, from Greek khrōs skin colour
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Encyclopedia Article for pleochroism

(from Greek pleion, "more," and chros, "colour"), in optics, the selective absorption in crystals of light vibrating in different planes. Pleochroism is the general term for both dichroism, which is found in uniaxial crystals (crystals with a single optic axis), and trichroism, found in biaxial crystals (two optic axes). It can be observed only in coloured, doubly refracting crystals. When ordinary light is incident on a crystal exhibiting double refraction, the light is split into two polarized components, an ordinary ray and an extraordinary ray, vibrating in mutually perpendicular planes. A dichroic substance such as tourmaline transmits only the extraordinary ray, having absorbed the ordinary ray (see ).

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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