Labradorescence Labradorite

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labradorescence in labradorite




video of labradorescence in labdradorite, visible angle of view changes.


labradorite can display iridescent optical effect (or schiller) known labradorescence. term labradoresence coined ove balthasar bøggild, defined (labradorization) follows:



labradorization peculiar reflection of light submicroscopical planes orientated in 1 direction (rarely in 2 directions); these planes have never such position can expressed simple indices, , not directly visible under microscope.



contributions understanding of origin , cause of effect made rayleigh (1923), , bøggild (1924).


the cause of optical phenomenon phase exsolution lamellar structure, occurring in bøggild miscibility gap. effect visible when lamellar separation between 128 252 nm (5.0×10 9.9×10 in); lamellae not parallel; , lamellar structure found lack long range order.


the lamellar separation occurs in plagioclases of composition, in particular, of calcic labradorite , bytownite (anorthite content of ~60 90%). requirement lamellar separation slow cooling of rock contains plagioclase. slow cooling required allow ca, na, si, , al ions diffuse through plagioclase , produce lamellar separation. therefore, not labradorites exhibit labradorescence (they might not correct composition and/or cooled quickly), , not plagioclases exhibit labradorescence labradorites (they may bytownite).


some gemstone varieties of labradorite exhibiting high degree of labradorescence called spectrolite.









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