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A gem’s shape refers to the face-up outline displayed
by the cut of a particular gemstone. In nature, the shape of a gemstone
is determined by its natural crystal structure and the conditions under
which the crystal developed. To enhance the natural beauty of the crystal
and provide suitable shapes for mounting, gem cutters form flat, symmetrical
planes, called facets, which catch and reflect light to emphasize preferred
colors, sparkle, and brilliance of the finished stone. In addition, gem
cutters try to select shapes and cutting styles which allow them to minimize
the appearance of undesirable flaws and to get the maximum weight from
the rough gem material. The most common shapes include round, oval, square,
triangle, pear, marquise, heart, and cushion. With diamonds, shapes other
than round are often referred to as fancy cuts. |
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Round Shape |
Square Shape |
Cushion Shape |
Trillion Shape |
Oval Shape |
Heart Shape |
Marque Shape |
Fancy Shape |
Pear Shape |
Octagon Shape |
Half-Moon Shape |
Hexagon Shape |
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Cutting Style |
Cutting style refers to the way in which a gemstone is cut or faceted.
Gemstone cutting is based on science. Each gem material has a known
refractive index which allows a gem cutter to determine how light rays
will bend as they pass through the stone. Using this information a
gemstone can then be precisely shaped to best enhance its natural beauty.
The styles of gem cuts are generally divided into faceted gems (gems
with geometrically shaped flat polished faces) and non-faceted gems
(those gems that do not have geometrically shaped flat polished faces
such as cabochons). The most common and basic cutting styles are as
follows:
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Cabochon Cut
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Has a dome-shaped top that is polished but un-faceted.
The term comes from a French word signifying a bald pate
(caboch, from the Latin cabo, meaning a head). Opaque,
asteriated, iridescent, opalescent, or chatoyant stones
are usually cut en cabochon. The back of a normal cabochon-cut
stone is flat, but it may be hollowed to lighten the color.
This is the simplest cut for a stone and is often seen
in antique jewelry. Since the cabochon is the simplest
style and often made from lower quality material that is
unsuitable for faceting, it generally costs less than faceted
stones.
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Step Cut
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Has rows of facets that resemble the steps of a staircase.
A step cut gem has sloping, four-sided elongated facets
that are cut below the table and run parallel to the stone’s
girdle. There are fewer facets in a step cut diamond than
in a brilliant cut stone. The baguette, a square-cornered,
rectangular stone is an example of a step cut. If step
cuts have clipped-off corners, they’re called emerald
cuts because emeralds are often cut this way. This protects
the corners and provides places where prongs can secure
the stone.
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Brilliant Cut
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Has mostly 3-sided facets which radiate outward from
the stone and are positioned so that the light coming through
them interplays in such a way to best enhance the stone’s
brilliance. Kite- or lozenge-shaped facets may also be
present.
The best-known example is the full-cut round brilliant,
which has 58 facets. Ovals, pears, marquises, and heart-shapes
can also be brilliant-cut. The single cut, which has 17
or 18 facets, is another type of brilliant cut. Square
brilliant cut stones are called princess cuts. Triangular
brilliant cuts are called trilliants. Gemstone pendants
or earrings are occasionally cut as briolettes. These have
a tear-drop shape, a circular cross-section, and brilliant-style
facets.
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Mixed Cut
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Mixed cuts include faceting elements from both the brilliant
and step cut techniques, either side by side or in different
areas of the gemstone. Mixed cuts are popular for colored
gemstones.
Fancy cut generally refers any cut which is not a standard
cabochon, brilliant cut, or step cut. A very common old-style
fancy cut is the rose cut which has brilliant-style facets,
a dome-shaped crown, a flat base and a round girdle outline.
Rose cut may also be cut with a pavilion. Other common
examples of fancy cuts are the checkerboard cut which is
step- and brilliant-cut with a large table facet on the
crown. Another example is the millennium cut which has
a step-cut crown and a pavilion with concave faceting.
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Antique Cushion |
Baguette |
Emerald Cut |
Briolette |
Pear Cut |
Common Cuts |
Marquise Cut |
Square Cut |
Trilliant Cut |
Round Cabochon |
Princess Cut |
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Evaluating a Well-Cut Gemstone
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Cut quality refers to the proportions and finish of the gemstone.
This is a crucial factor because it affects the brilliance and color
of gems, but its importance is not always reflected in the price of
colored gemstones. Our Todaygem.com gemologists have put together a
couple of handy tips to help you quickly evaluate a gemstone’s
quality.
- View your gemstone face up and see whether it exhibits even color
distribution all across the stone. Well-cut stones do not display
large black areas or any washed out areas that allow you to see right
through them. In general, the larger the window, the poorer the cut.
Even color distribution is normally a sign of good quality cut.
- Examine the entire shape of the gemstone and consider it to its
carat weight. If you were to compare two stones with the same face-up
size, the one that has a deeper and fatter bottom will weigh considerably
more than a well-cut stone with a more shallow bottom. The overly
deep stone would potentially cost more, even though it has the same
face-up size; however, it may be impractical for mounting and appear
overly dark.
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