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Shape
Diamonds do not show all of their beauty as rough stones;
instead, they must be cut and polished to exhibit the characteristic
fire and brilliance that diamond gemstones are known for. Diamonds
are cut into a variety of shapes that are generally designed to
accentuate these features.
Diamonds which are not cut to the specifications of Tolkowsky's
round brilliant shape (or subsequent variations) are known as "fancy
cuts." Popular fancy cuts include the baguette (from the French,
meaning rod or loaf of bread), marquise, princess (square outline),
heart, briolette (a form of the rose cut), and pear cuts. Generally
speaking, these "fancy cuts" are not held to the same strict
standards as Tolkowsky-derived round brilliants and there are less
specific mathematical guidelines of angles which determine a
well-cut stone. |
Cuts are influenced heavily by fashion: the
baguette cut—which accentuates a diamond's luster and
downplays its fire—was all the rage during the Art Deco
period, whereas the princess cut—which accentuates a
diamond's fire rather than its luster—is currently gaining
popularity. The princess cut is also popular amongst diamond
cutters: of all the cuts, it wastes the least of the
original crystal. The past decades have seen the development
of new diamond cuts, often based on a modification of an
existing cut. Some of these include extra facets. These
newly developed cuts are viewed by many as more of an
attempt at brand differentiation by diamond sellers, than
actual improvements to the state of the art.Quality
The quality of a diamond's cut is widely considered the
most important of the four Cs in determining the beauty of a
diamond; indeed, it is commonly acknowledged that a well-cut
diamond can appear to be of greater carat weight, and have
clarity and color appear to be of better grade than they
actually are. The skill with which a diamond is cut
determines its ability to reflect and refract light.
In addition to carrying the most importance to a diamond's
quality as a gemstone, the cut is also the most difficult to
quantitatively judge. A number of factors, including
proportion, symmetry, and the relative angles of various
facets, are determined by the quality of the cut and can
affect the performance of a diamond. A poorly cut diamond
with facets cut only a few degrees out of alignment can
result in a poorly performing stone. For a round brilliant
cut, there is a balance between "brilliance" and "fire."
When a diamond is cut for too much "fire," it looks like a
cubic zirconia, which gives off much more "fire" than real
diamond. A well-executed round brilliant cut should reflect
light upwards and make the diamond appear white when viewed
from the top. An inferior cut will produce a stone that
appears dark at the center and in some extreme cases the
ring settings may show through the top of the diamond as
shadows.
Several different theories on the "ideal" proportions of a
diamond have been and continue to be advocated by
professional gemologists. Recently, there has been a shift
away from grading cut by the use of various angles and
proportions toward measuring the performance of a cut stone.
A number of specially modified viewers and machines have
been developed toward this end. They included the FireScope,
a.k.a. SymmetriScope or IdealScope (tests for light leakage,
light return and proportions), Hearts and Arrows Viewer
(test for "hearts and arrows" characteristic pattern
observable on stones exhibiting high symmetry), GemEx
BrillianceScope (tests for direct light performance results
of a diamond), Isee2 Machine (tests for diffused light
performance results of a diamond), and ASET (test for AGS
cut grade). These viewers and machines often help consumers
determine the light performance results of the diamond in
addition to the traditional 4 C's. Along with this shift
there are a few companies that provide results on these
viewers and machines in addition to the original 4c's. The
GIA has also developed criteria for grading the cut of round
brilliant stones.
The cutting process
The process of shaping a rough diamond into a polished
gemstone is both an art and a science. The choice of cut is
often decided by the original shape of the rough stone,
location of the inclusions and flaws to be eliminated, the
preservation of the weight, popularity of certain shapes
amongst consumers and many other considerations. The round
brilliant cut is preferred when the crystal is an
octahedron, as often two stones may be cut from one such
crystal. Oddly shaped crystals such as macles are more
likely to be cut in a fancy cut—that is, a cut other than
the round brilliant—which the particular crystal shape lends
itself to.
Even with modern techniques, the cutting and polishing of a
diamond crystal always results in a dramatic loss of weight;
rarely is it less than 50%. Sometimes the cutters compromise
and accept lesser proportions and symmetry in order to avoid
inclusions or to preserve the carat rating. Since the per
carat price of diamond shifts around key milestones (such as
1.00 carat), many one-carat diamonds are the result of
compromising "Cut" for "Carat." Some jewelry experts advise
consumers to buy a 0.99 carat diamond for its better price
or buy a 1.10 carat diamond for its better cut, avoiding a
1.00 carat diamond which is more likely to be a poorly cut
stone.
Cleaning
Although it is not one of the four Cs, cleanliness
affects a diamond's beauty as much as any of the four Cs. A
clean diamond is more brilliant and fiery than the same
diamond when it is "dirty." Dirt or grease on the top of a
diamond reduces its luster. Water, dirt, or grease on the
bottom of a diamond interferes with the diamond's brilliance
and fire. Even a thin film absorbs some light that could
have been reflected to the person looking at the diamond.
Colored dye or smudges can affect the perceived color of a
diamond. Historically, some jewelers' stones were misgraded
because of smudges on the girdle, or dye on the culet.
Current practice is to thoroughly clean a diamond before
grading its color.
Maintaining a clean diamond can sometimes be difficult, as
jewelry settings can obstruct cleaning efforts, and oils,
grease, and other hydrophobic materials adhere well to a
diamond's surface. Some jewelers provide their customers
with ammonia-based cleaning kits; ultrasonic cleaners are
also popular.
Cleanliness does not affect the diamond's market value, as
any competent jeweler will clean the diamond before offering
it for sale. However, cleanliness might reflect a diamond's
sentimental value: some jewelers have noted a correlation
between ring cleanliness and marriage quality. |