B
Bar channel setting
Individual metal bars separate the gemstones.
The metal is molded around a gem to lock it in place.
Baroque pearl
A shape of pearl. The shape is not round
but is symmetrical, having similar characteristics on opposite
sides.
Bezel setting
A metal rim gently secures a gemstone
in place by the girdle. The bezel setting guards the gem from
damage, yet does not block light from creating brilliance.
Blemish
A flaw (blister or spot) on the surface
of a gem.
Brilliance
White light reflected up through the
surface of a diamond. Brilliance is maximized by cutting a diamond
to the correct proportions.
Brilliant cut
Any cut with 58 facets. A brilliant cut
can have several shapes: round, oval, radiant (basically square),
as well as pear-shaped or heart-shaped.
Birthstone
Birthstones have their roots in ancient
astrology, and there have been many birthstone lists used over
the years. The most common one today is based on a list first
publicized by the U.S. jewelry industry in the 1950s.
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C
Cameo
A style of carving in which the design
motif is left and the surrounding surface is cut away leaving
the design in relief. Cameos in jewelry are often made of shell,
although hard stone cameos such as sardonyx are more valuable.
Cameos have been carved from ancient times, and ancient motifs
such as the goddess Athena or a Baccante or follower of Bacchus
were popular cameo subjects in Victorian times, through the
1930's. Cameos are still being made today in Italy. A cameo
habille is one in which "jewelry" such as a miniature
diamond pendant is actually attached to the carving.
Cabochon
A gemstone shape resembling a dome. Onyx
is commonly cut in a cabochon shape, as are star sapphires.
Carat
A unit of weight for a diamond, equivalent
to 200 milligrams, or 0.2 gram.
Center stone
The central, dominant stone in a piece
of jewelry set with multiple stones. In a ring set with one
stone, the center stone is also called the solitaire.
Chemistry
It is the chemistry of a gem material
which is ultimately responsible for all of its physical properties.
Chemistry determines color which in turn determines value. Heat
treatment is a chemical modification of a gem material to improve
it?s color and value.
Channel setting
Ridges in the metal create a channel
that holds gemstones in place.
Choker
A pearl necklace 16 inches long.
Clarity
The clarity scale is used to describe
how few inclusions a gemstone has. For diamonds, the clarity
scale ranges from flawless (FL), meaning a gemstone has no internal
or external flaws, to severely included (I3), meaning there
are many flaws clearly visible to the unaided eye.
Cloud
A cluster of small inclusions inside
a gemstone.
Color
The color scale is used to describe the
color tones of a gemstone. For diamonds, the color scale ranges
from D, meaning completely colorless, to Z, which indicates
a distinct yellow cast. As the scale moves from D to Z, it indicates
increasing levels of yellow and brown tone. For color gemstones,
the color is measured by tone and hue. Color is the most important
criteria in determining the value a colored gemstone. More important
than clarity and cut, even subtle differences in hue can correspond
with marked variations in valuations
Comfort fit
The rounded finish on the inside of
a ring's band. This design does not pinch the skin of the finger
as much as other ring bands and provides comfort for constant
wear.
Corundum
A hard mineral that exists in the form
of colored crystals, such as rubies and sapphires.
Crown
The edges of a gemstone above the girdle
and surrounding the table. Colored light escapes through the
crown in the form of fire.
Crystal
The protective clear cover that fits
over the watch dial. It can be made of mineral, synthetic sapphire,
plastic, or acrylic material. The sapphire crystal is the most
durable, as only a diamond can scratch its surface.
Crystal System (Group)
Crystals are divided in to 7 systems,
each corresponding to a specific set of angular, geometrical,
and symmetrical specifications. Every gem group can be classified
according to its crystallization. The study of crystallization
is invaluable in the determination and identification of rough
gem materials.
Culet
The facet at the tip of the pavilion
of a gemstone. The culets of older, European-cut diamonds can
be seen through the table of the diamond and appear as round,
glassy disks. The preferred culet is visible only as a tiny
focal point where the facets of the pavilion converge.
Cultured pearl
A pearl cultivated by artificial insertion
of a small irritant (often a bead made of mother-of-pearl and
mantle tissue taken from a particular species of oyster found
on the Mississippi River) into an oyster or other bivalve mollusk.
The method of culturing pearls was patented by Kokichi Mikimoto
in 1916.
Cut
Refers to the geometric proportions of
a gemstone. The cut of a gemstone is one of the most important
factors in determining how much sparkle a gemstone produces.
Cut, ideal
A diamond cut of perfect proportions,
having depth percentages and table percentages that maximize
fire and brilliance.
Cut, very good
A grade of diamond cut that fits very
strict requirements for depth percentage and table percentage.
These specific proportions maximize fire and brilliance in a
diamond.
Cut, good
The cut grade assigned to diamonds with
acceptable proportions. These diamonds generally have very good
brilliance and fire and they are also are beautiful in jewelry.
Cut, fair
The cut used to maximize the weight
of a diamond, generally at the expense of fire and brilliance.
Diamonds with this cut are less expensive than diamonds having
good and very good cuts, and they lack the sparkle people expect
from a diamond.
Cut, poor
This cut makes diamonds appear lifeless.
These diamonds are not recommended for fine jewelry.
Cut , european
The style of diamond cutting popular
from approximately 1890 to the 1930s. Unlike the old mine cut
preceding it, the European cut has a round girdle (perimeter)
made possible by the introduction of the power bruting machine
(Bruting is the term for shaping the girdle of a diamond, the
first step in the cutting process). The European cut can be
distinguished by the size of the table (the top, flat facet)
in relation to the diameter of the stone. In a European cut,
the table is smaller in relation to the diameter of the stone.
Also, the culet (the bottom facet, is often large, often appearing
to create a hole at the bottom of the diamond, when viewed from
the top, since the large culet lets light escape instead of
reflecting back to the viewer.
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D
Depth
The height of a gemstone measured from
the culet to the table.
Diameter
The width of the diamond, as measured
across the widest part of the girdle.
Depth percentage
The height of a gemstone, measured from
the culet to the table, divided by the width of the gemstone.
The depth percentage is critical to creating brilliance and
fire in a diamond, and a gemstone with a depth percentage too
low or too high will lack sparkle.
Doublet
A form of gemstone trickery that was
devised to allow inexpensive materials to imitate the more valuable
gemstones before modern synthetics were available. A doublet
can take several forms but always involves a fake gemstone produced
by gluing together two different materials to form an illusion.
A very common one in Victorian times was the garnet and glass
doublet. This involved a red garnet top, glued to a colored
glass bottom. The refractive properties of a faceted stone are
such that the red of the garnet only shows at odd angles, or
if the stone is immersed in a special liquid with a high refractive
index. Thus, for example, a green glass bottom with a garnet
top will give the appearance of a fine emerald because the top
is a natural gemstone with cut facets, and a few natural imperfections,
and the bottom is bright green which reflects throughout the
stone. The effect is hard to appreciate unless you've seen one.
Density
Water has a density of 1gram/cc. Density
is the weight of a material as compared to an equal volume of
water.
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E
Enhancements
Treatments, such as heating and oiling,
that are an accepted part of the process of gemstone cutting
and polishing. The AGTA only approves of enhancements that are
permanent, do not counterfeit the beauty of the gem, and only
tap the natural potential beauty of the gem.
Eye-clean
A gemstone with no inclusions visible
to the unaided eye.
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F
Facet
The flat polished surfaces on a gemstone.
A round, brilliant-cut diamond has 58 facets.
Fire
The colored light reflected from within
a diamond through the crown. Fire is maximized by cutting a
diamond to the correct proportions.
Fluorescence
A glow, usually of a bluish color, that
emanates from some diamonds when exposed to ultraviolet light.
Strong fluorescence is not desirable, but faint fluorescence
does not affect the appearance of a diamond.
Fresh-water pearl
A pearl produced by a mollusk that inhabits
freshwater, usually these pearls are shaped like an uneven grain
of rice. There is also a variety called Tennessee fresh water
pearls that taper like a long tooth.
Fob
A short chain with a decorative seal
or other device attached to the end. The fob and chain hung
outside watch pocket, and could be used to pull the watch out
of the pocket.
Foilback
A method of coating the back of a stone
with silver, gold, or colored foil. This enhances the brilliancy
of the stone, by reflecting back as much light as possible.
It is commonly seen in costume jewelry. A foilbacked rhinestone
whose foil has been damaged (often from water creeping in) does
not sparkle anymore and is said to be a "dead" stone, lowering
the value of the piece. Before, modern, highly reflective cuts
were developed, even diamonds were foilbacked.
French Jet
Black glass fashioned to imitate real
jet. Glass is heavier than real jet, and can feel cold to the
touch compared to real jet.
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G
GIA
The Gemological Institute of America,
or GIA, is recognized as a top authority on grading gemstones.
Girdle
The narrow band around the widest part
of a diamond. The setting in a piece of jewelry usually grasps
the diamond around the girdle.
Grade
Gemstones are frequently sent to an independent
laboratory such as the GIA, AGS, NGL, or AGTA to be graded against
a master set of gemstones, according to an industry-wide common
set of grading guidelines. These grades are compiled to form
a complete appraisal which offers an assessment the worth of
a gemstone.
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H
Head
The part of the setting that holds the
center stone or solitaire in place.
Hardness
The part of the setting that holds the
center stone or solitaire in place.Moh's scale of hardness is
useful for comparing the relative hardness of different gem
materials. The values are as follows:
