DIFFERENCES IN
APPEARANCE DUE TO SOURCE AND
INTENSITY OF LIGHT
The appearance of a gemstone's
color changes drastically under
different sources and intensities
of light. Many of us have had
the experience of having a
dark blue suit or handbag appear
black indoors, only to realize
its true color when outside
under sunlight. With gemstones,
the difference is even more
pronounced. The appearance
of a gemstone's color will
change depending upon the strength
of the light entering the stone,
as well as the type of light.
Compared to its appearance
under north light (natural
light entering a room through
a north-facing window) at noon
on a sunny day, a ruby's quality
will seem to diminish by more
than half when viewed in the
evening or on a rainy day.
Rather than simply appearing
darker in color, the gemstone
will appear to have lost its
beauty altogether. Professional
gem dealers make quality judgments
by comparing gems to "master" stones
(reference stones) that serve
as a standard, allowing them
to judge quality without error
even when conditions change.
However, judgments made by
inexperienced dealers or others
who rely on gut feeling are
questionable. Reputable gemstone
dealers around the world -
whether in New York, Geneva,
or Tokyo - will always establish
quality through comparison
with master stones or company
inventory.
The beauty of rubies is most
apparent when seen under incandescent
light, just as dishes laid
out on the dining table look
more appetizing under incandescent
light. Under fluorescent light,
both rubies and food lose their
appeal, and their beauty is
halved. Gems with reddish and
orangey colors appear to lose
their beauty under fluorescent
lighting, making it difficult
to compare their qualities.
Conversely, bluish gemstones
such as sapphire and aquamarine
look more attractive under
fluorescent lighting than under
incandescent light. It is easier
to compare the quality of such
gemstones under fluorescent
lighting, as even slight differences
can be perceived clearly.
As shown in these photographs,
the same rubies will appear
to have different colors depending
upon the light source, such
as (1) north light on a sunny
day, (2) sunlight on a rainy
day, (3) incandescent light,
and (4) fluorescent light.
When confirming the color of
a gemstone indoors, it is best
to do so using a combination
of incandescent and fluorescent
lighting. |
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| 1.North
light on a sunny day |
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| 2. Sunlight
on a rainy day |
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| 3.Under
incandescent light |
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| 4.Under
fluorescent light |
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Size
(mm):Diameter3-4
Mong Hsu Ruby, Heated
Gem Quality |
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JUDGING
QUALITY
The first impression of beauty is
very important. A gemstone that gives
an impression of beauty just at a
glance does so because of a high
degree of transparency, a balanced
and distinct mosaic pattern throughout
the stone, and a fine overall appearance.
There is a tendency for the French
to prefer dark rubies (tone levels
7 to 6), while the Italians and Japanese
prefer lighter stones (tone levels
5 to 4). In Bangkok, where buyers
gather from around the globe, high
prices are seen over a wide range
of attractive stones, reflecting
the variety of tone preferences among
nationalities. It is apparent that
tone defines the balance between
supply and preference-based demand.
Finally, regarding the judging of
imperfections, it is important not
to be overly concerned with those
that are not eye-visible, as long
as they are not defects or do not
adversely affect durability. However,
deciding the acceptable degree of
surface imperfections and scratches
visible under 10x magnification,
as well as other standards of finish
quality, is the responsibility of
the professional jeweler. |
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