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Glossary - Definitions
All diamonds share certain features that allow us to compare and evaluate them. These features are called the 4Cs: Carat weight, Clarity, Color and Cut.
In this setting, the stone is secured in the mounting by a thin
strip of metal surrounding the stone's perimeter.
A term used to describe external characteristics on
the surface of a diamond, such as: nicks, scratches,
polish marks, abrasions, naturals and extra facets.
Intensity of the internal and external reflections of
white light returned to the eye through the crown of
a diamond. Proportions, polish, symmetry, clarity and
overall workmanship all affect a diamond's brilliance.
A style of cut of a round stone, where triangular and kite-shaped
facets emanate from the center of the stone to
the girdle edge on both the crown and pavilion.
The standard unit of weight, not size, used for
gemstones. One carat is equal to 0.200 grams.
Carat weight alone does not determine a diamonds
value. Two stones of equal weight can vary widely
in price because of quality differences. In fact, a
smaller diamond may actually be more beautiful
than a larger stone with inferior cut, clarity, color
or presence.
When considering diamonds of equal quality, the
larger stone will have considerably more value.
Usually, a two-carat diamond will be more than
twice as valuable as a one-carat stone.
The word 'carat' comes from the carob tree whose seed was used as the standard of weighing precious stones.
Less than 5% of all the diamonds made into jewelry are larger than one carat.
A setting style, where two parallel metal walls are
used to hold gemstones in place, with no metal
between each stone.
Shallow break on a diamond that extends from either
a girdle edge or a facet junction. A chip is considered
an internal clarity characteristic, and can pose a durability concern.
A term used to describe the relative absence
of inclusions and blemishes in a gemstone.
A diamond's clarity rating has a direct effect on
a diamond's beauty and price.
Virtually all diamonds have imperfections called
inclusions and blemishes. A stone is said to be
'flawless' if, under ten-power magnification, no
external imperfections are visible and no internal
flaws are visible. A truly flawless diamond is extremely
rare and priced accordingly.
All gem-grade diamonds can receive a clarity rating
based on an industry standard scale: FL (flawless)
to I3 (heavily included).
A type of inclusion composed of numerous
pinpoints. Pervasive clouds can cause a hazy
or milky appearance in a diamond.
The basic hue (body color) of a diamond
when brilliance and dispersion are ignored.
The saturation of color is judged against
a predetermined scale.
The colored tinting found in most diamonds is
caused by minute impurities within the stone.
The untrained eye is incapable of making the
color evaluations that can affect the value of
a stone by thousands of dollars.
The color of each diamond is determined by comparing it to
authenticated 'master diamonds'. Each stone is
then color-graded to a precise scale from 'D' (colorless) to 'Z' (saturated).
The part of a diamond above the girdle plane.
Small, octagonal facet on the point of the pavilion
on some brilliant-cut diamonds or a rectangular facet
on the keel of some step-cut diamonds.
Term used to describe a diamond with a rectangular or
squarish girdle outline, curved sides, rounded corners
and brilliant-cut facets. Another name for oval cut.
Cut refers to the facet proportions on the
surface of a diamond, its polish and symmetry. More than any other factor,
the precision of its facets determines the
beauty of the stone.
There is a tradeoff between qualigy and size.
When a stone is cut to maximize brilliance,
dispersion and scintillation, it usually loses size.
More of the stone must be cut away. Conversely,
when cut for size, the diamond usually loses
brilliance, dispersion and scintillation.
The breakup or separation of white light into spectral
colors, each having its own wavelength and frequency.
Synonymous with 'fire'.
Rectangular or square step-cut stone with
diagonally cut corners and two, three or four
rows of facets parallel to the girdle on the
crown and pavilion.
An unnatural process that alters the appearance,
particularly the color or clarity, of a natural diamond
or other gemstone. Coating, irradiation, high
temperature/high pressure, fracture filling and laser
drilling are all examples of enhancement. The only
acceptable enhancements are cutting and polishing.
Synonymous with 'treatment'.
Flat, polished surface on a fashioned gemstone.
Any shape other than a round-brilliant or single cut.
Includes: , pear, marquise, oval and heart
shapes.
Any cleavage or fracture on or below the surface
of a gemstone. The appearance is usually white when
viewed at a right angle to the break.
Quality of a diamond's polish, condition of its girdle,
and the precision of the faceting arrangement.
The breakup or separation of white light into spectral
colors, each having its own wavelength and frequency.
Synonymous with 'dispersion'.
A diamond can be fashioned with a shallow pavilion
and large table, to give the impression of a much larger
stone. This technique produces a dull stone, and even
worse, it creates an ugly 'fisheye' effect when viewed
through the crown.
Emission of visible light by a material when it
is exposed to certain energy sources, such as
radiation or ultraviolet light. Fluorescence only
continues as long as the material is exposed
to the energy source.
The popular and overly simple four factors: cut,
clarity, color and carat weight, which are commonly
used to determine the value of a diamond. These
factors alone are an insufficient measure of a
diamond's true quality, beauty and value.
The narrow band that circumscribes the edge of
the plane intersecting the crown and pavilion of a
diamond. The girdle may be polished, faceted or
bruted (rough surface).
Internal or external lines commonly found on a
diamond which show the growth pattern of the
crystal structure. Grain lines are often the result of
growth inconsistencies and cannot be removed
by recutting the diamond. Significant graining can
severely affect the beauty of a diamond.
Any internal clarity characteristic of a diamond. Large or numerous inclusions are considered flaws that seriously diminish the value of a gem.
Virtually all diamonds have imperfections called
inclusions and blemishes. A stone is said to be
'flawless' if, under ten-power magnification, no
external imperfections are visible and no internal
flaws are visible. A truly flawless diamond is extremely
rare and priced accordingly.
All gem-grade diamonds can receive a clarity rating
based on an industry standard scale: FL (flawless)
to I3 (heavily included).
A diamond crystal within another diamond crystal.
Such inclusions are considered flaws and often cause
a problem with the overall polish of the diamond
and cannot be easily removed.
The result of an enhancement process used
to improve the appearance of a diamond with
dark or black inclusions. A laser is used to drill
a hole to reach the inclusion surface where it
can then be bleached with acid.
Elongated brilliant-cut with two curved sides
and two pointed ends.
A set of polished diamonds of known body color and
saturation to which other diamonds can be compared
to assess their color grade.
A finishing detail on metal work that produces
a beaded effect along the edge of the metal.
A type of faceting arrangement which features varying
rectangular girdle outlines and cut corners with the
number of facets greater or less than the standard 57
or 58 found on a round-brilliant.
See setting.
When the pavilion of a diamond is too deep, a darkening
'nailhead' effect appears in the middle of the stone.
A portion of the original surface of the rough
diamond which has been left on a polished
diamond. This practice maximizes carat weight
but may compromise beauty.
A brilliant-cut diamond with an elliptically shaped
outline having two curved sides and two rounded ends.
The portion of a diamond below the girdle,
including the culet.
A brilliant-cut diamond with a pear-shaped outline
having two curved sides, one rounded end and one
pointed end.
The overall condition of a facet's surface on
a fashioned diamond.
This evaluation includes precision
of cut, symmetry and polish. Individually, and as
a group, they influence a diamond's beauty and
overall appearance.
The shape, size and angle of each individual facet is
crucially important. The expert diamond cutter must
follow a prescribed geometric plan to produce an
'excellent' precision of cut. If the cutter fails, Tiffany
will quickly find the mistake and reject the stone.
The quality of a stone's polish directly influences
a diamond's brilliance, dispersion and scintillation.
Part of the metal setting designed to hold the
diamond in place. Tiffany & Co. uses six prongs
to hold one round-brilliant in place.
The relative dimensions and angles of a diamond's
faceting and the relationships that exist between them.
Rough diamonds are those that are mined, before they are cut and polished.
A traditional diamond shape based on the octahedron
rough crystal. It has 57 or 58 facets consisting of
a crown, girdle and pavilion. The crown has a table,
8 kite-shaped bezel facets, 8 star facets, and 16
triangular upper-girdle facets. The girdle
circumscribes the diameter and may be either faceted
or bruted. The pavilion contains 8 kite-shaped main
facets, and 16 triangular lower-girdle facets. It may
or may not have a culet on the pavilion.
The flashes of reflective light emanating from a
diamond's polished facets are observed when either
the diamond or light source is moved. Scintillation
is often referred to as 'sparkle'.
The entire metal mounting holding the polished
diamond or diamonds. The design and workmanship
of the setting is critical to the overall beauty
of a diamond ring. Synonymous with 'mounting'.
The face-up girdle outline of a polished diamond
or gemstone.
A setting style in which a pair of centrally positioned
prongs holds two stones: one to its right and one
to its left.
A cutting style in which narrow, rectangular diamond
facets are arranged in rows parallel to the girdle on
both the crown and pavilion.
A term used to describe the precision and exactness
of the facet placement on a polished diamond.
The large facet in the center of the crown of a polished
diamond. On a round-brilliant-cut diamond, the table
is octagonal in shape.
Trapezoid shaped cut diamonds, usually placed at the sides of a solitaire, or in ensembles of diamonds on a jewel.
Light containing a balanced mixture of all wave-
lengths in the visible portion of the electromagnetic spectrum, to include: red, orange, yellow, green,
blue, indigo and violet.
Because carat weight is always a factor in pricing, some
diamond cutters will attempt to trick casual buyers. For
example, by creating an excessively thick girdle, carat
weight (and price) is increased. Brilliance and beauty
are, of course, noticeably impaired.
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TABLE OF CONTENTS
What is a diamond
Material properties
Natural history - How diamond is formed
History of diamonds
The diamond industry
Blood diamonds
Glossary
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