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FIRE IN THE EARTH
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Perhaps
that is too complicated. Let us put it simply this way, even though we
intend to consider it in more interesting fashion later with the
discussion of diamond cutting and faceting: The optical properties of
the diamond have to do with the tricks the diamond plays with light.
Refraction means bending a light ray when it passes from the air into
a dense substance such as water, glass, or diamond. Entering the
diamond from the top, for instance, at an angle, the light is always
bent downward. A common example of this is seen when you thrust a
straight stick into a pool of water. The stick appears to be bent at
the surface of the water. Every transparent substance bends light a
different amount, and this property is measured by a number called the
"index of refraction." We said the diamond has the highest index of all
gem stones. This comparison table will prove it:
Diamond.............................. 2.42
Zircon................................. 1.95
Sapphire, ruby.......................... 1.77
Topaz ................................. 1.62
Emerald............................... 1.59
Flint glass.............................. 1.58
Quartz ................................ 1.55
Ice ................................... 1.31
This,
of course, definitely affects the brilliance of a gem. Any stone which
is highly refractive has the power of gathering light—light coming
from all directions—which is bent into the center of the diamond, the
diamond thus acting as a veritable magnet of light. A ray of light
striking a diamond is split into a band of colors ranging from red to
violet, because a cut diamond, like a glass prism, has the power to
separate the light into rainbow hues. The spectrum produced by the
prism, however, is a comparatively
(12)
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