 Labradorite
is truely a fascinatingly beautiful mineral.
Its a mineral whose charm is not fully noticed
and may be overlooked if not viewed from
the proper position. Generally a dull, dark
looking mineral with no special virtue until
the colorful shiller is observed glowing
on the surface. Labradorite can produce
a colorful play of light across cleavage
planes and in sliced sections called labradorescence.
The usually intense colors range from the
typical blues and violets through greens,
yellows and oranges. Some rare specimens
display all these colors simultaneously.
The color display is from lamellar intergrowths
inside the crystal. These intergrowths result
from compatible chemistries at high temperatures
becoming incompatible at lower temperatures
and thus a separating and layering of these
two phases. The resulting color effect is
caused by a ray of light entering a layer
and being refracted back and forth by deeper
layers. This refracted ray is slowed by
the extra travel through the layers and
mixes with other rays to produce a light
ray coming out that has a different wavelength
than when it went in. The wavelength could
correspond to the wavelength of a particular
color, such as blue. The effect depends
on the thickness and orientation of the
layers. If the layers are too thick or too
thin no color shiller is seen. Also if the
viewer does not observe from the precise
angle or if light is not supplied from the
proper angle then no color shiller is seen.
The labradorescence is truely a one of a
kind mineralogical experience and must be
observed in person in order to truely appreciate
its beauty
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