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How to Tell Color Enhanced Diamonds
from Natural Color Diamonds
Color enhanced diamonds are visibly different from
any natural colored stones such as rubies or sapphires. Their diamond
brilliance easily sets them apart.However telling color enhanced diamonds
from natural color diamonds is not so easy. In fact, you can’t
tell the two apart just by looking at them. For that, you need an
assistance of professionals. |
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| Professional Methods of Identifying
Colored Diamonds |
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| The two main methods of identifying color-enhanced diamonds
are color zoning
and spectroscopy.
Color zoning will
provide an indication of probable color enhancement, but only
spectroscopy, a procedure done in a trade lab by a trained gemologist,
will give a conclusive answer on the origin of color of the
diamond. |
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| Color Zoning |
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| The color in an enhanced diamond is usually evenly distributed
throughout the diamond. In some instances, there is an uneven
coloration that can be seen using a microscope or a loupe to
be directly related to the faceted shape of the diamond. In
certain stones the overall color seen through the pavilion is
much lighter than the face-up color of the stone with color
occurring in a narrow area near the culet or keel-line with
no other strong color zoning seen through the rest of the stone.
Such uneven or zoned coloration is caused by the irradiation
process is most often seen as a band of dark blue, green or
yellow color that parallels the outer faceted shape of a diamond
or a band of color that forms a star-shaped pattern around the
pointed culet of a diamond. This is a strong indication of enhancement. |
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| Spectroscopy |
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An infrared spectrophotometer, or spectroscope, is the instrument
used to record the diamond’s absorption spectrum. The
recorded spectrum is then studied for absorption lines –
features that show whether a diamond has been enhanced or not.
The presence of the H1b (1,936 nm) and H1c (2,026 nm) absorption
lines is a tell-tale sign that the diamond was color enhanced.
However, these lines can be eliminated if the diamonds are exposed
to over 1400 C? heat – and some manufacturers have attempted
to pass their enhanced stones as natural-color, by superheating
them and eliminating these lines. However, heating diamonds
at such high temperatures results in the stones having an unattractive
green color and, sometimes, frosted facets. In short, it’s
not possible to eliminate the H1b and H1c absorption lines without
seriously lowering the quality of the stones in the process.
Green Diamonds
- The origin of color in some green diamonds cannot be determined
as being natural or enhanced because both are made using the
same process – irradiation – one occurring naturally
under the ground, the other, in a lab. A trained gemologist
has to look for brown or green irradiation stains on the surface
to determine if it is a natural body color. But sometimes these
stains can be removed during the cutting process thereby putting
even a certain natural stone’s origin of color in doubt. |
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