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Diamond 4
The influence of weight Although
a diamond weighing
over 3000 carats has been found, rough diamonds of con siderable
weight are extremely rare. Still rarer are heavy cut diamonds,
given that the average loss of weight in the cutting process
is more than 60 percent. All else being equal, a diamond twice
the weight of another is much rarer and therefore much more
precious and will have a higher price per carat. Weight also
has psychological as well as scarcity value: a diamond of
1 carat or slightly more is worth more weight for weight than
one of 0.9 carats because it exceeds the conventional limit
of the complete carat. The same applies at the dividing line
for 2 carats, 3 carats, and so on (Fig. B). In short, the
price per carat increases by stages with each complete carat
number, up at least to a weight of about 10 carats, after
which the effect is negligible, although such large diamonds
are extremely uncommon.
The influence of color The
vast majority of diamonds are colorless, or yellowish, ranging
from a barely perceptible tinge to straw-yellow. Perfectly
clear stones, however, are comparatively rare, but the effect
of dispersion in diamonds is more pleasing on a clear ground
than on a yellowish one. For these, plus psychological reasons,
the more or less perfectly colorless stones are in greater
demand; and value diminishes with an increase in yellow (or
more rarely, brown) coloration.
In an effort to quantify this, scales of colors
of different intensities were established, with names of the
color categories relating to the principal localities in which
diamonds of that color were found, or to other factors. Thus
the main diamond trading centers evolved roughly similar color
codes matched by approximate sets of values. A very precise
scale has more recently been introduced in the United States,
with grades distinguished by letters of the alphabet (beginning
with D, not A) and referring to data supplied by special measuring
instruments rather than the naked eye. Over the last few years,
European scales have been adapted to that of the United States,
a series of sample diamonds being used for purposes of comparison.
The four scales most widely used today and in the recent past
are shown in Fig. C (4b is the same as 4a, but with the old
nomenclature of 1).
The correspondence between scales 1 and 2 is
approximate, as is their relationship to the others, whereas
4a and 4b were designed to be cross-referenced. As a general
guide, color H (white) is very good and few diamonds can boast
such quality. Color I (the old "commercial white")
is much better than this name would.imply, with a barely perceptible
yellow tinge; and many stones on the market, particularly
medium- or large-sized ones, come under categories J, K, L,
or M. By contrast, "rare white" stones are much
less frequent. A very rough idea of the visibility of coloration
in diamonds of different gradcs (seen from above only, in
conditions of "use, rather than the ideal conditions
according to which they are classified) can be obtained from
which uses the classifications of the CIBJO scale.
Naturally, the larger the area over which any
coloration is viewed, the easier it is to see. All else being
equal, the price of diamonds varies quite sharply with color.
Again, as a rough guide and obviously depending on the state
of the market, if a diamond with certain characteristics and
weight of color H were worth 100, another with the same characteristics
of color F could be worth 130, while one of color J would
be worth 80, and one of color M
1 -
2 - 3 - 4
- 5
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