value factors
Features used to judge the quality and value of all gemstones.
four c s
Four value factors (clarity, color, cut, and carat weight) that describe the quality
of a finished diamond.
inclusions
Clarity characteristic totally enclosed in a polished gemstone or extending into it
from the surface.
blemishes
Clarity characteristic that’s confined to the surface of a polished gemstone.
clarity characteristics
The collective term for inclusions and blemishes.
lab-grown gem
A manmade (synthetic) gem with essentially the same chemical composition, crystal structure, and properties as its natural counterpart.
simulant
A natural or manmade material that resembles a gem (also called imitation).
yag (yttrium aluminum garnet)
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ggg (gadolinium gallium garnet)
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brightness
The effect of all the diamond’s internal and external reflections of white light.
fire
The flashes of color you see in a polished diamond.
scintillation
The flashes of light and the contrasting dark areas you see when the diamond, the
light, or the observer moves.
crown
Top part of the gem above the girdle.
girdle
The narrow section of a finished gem that forms the boundary between the crown and
the pavilion and functions as the gem's setting edge.
pavilion
Lower part of a faceted gem below the girdle.
facets
A flat, polished surface on a finished gem.
culet
Small facet at the bottom of a finished gem.
brilliant cut
Cutting style with triangular or kite-shaped facets that radiate from the center toward
the girdle.
standard round brilliant
A round brilliant-cut stone with 57 or 58 facets. Often called a full cut.
single cuts
A round stone with 17 or 18 facets.
fancy cuts
Amy gemstone shape other than a standard round brilliant.
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step cuts
A cutting style that features long, narrow facets in rows parallel to the girdle on
both the crown and pavilion.
A small, four-sided step cut that's rectangular, square, or tapered.
mixed cuts
Cut that combines brilliant-cut and step-cut styles.
branded cuts
Cutting style that’s developed, named, and promoted by a specific manufacturer.
metric carat
The international unit of measurement for gem weight. One carat equals one-fifth of
a gram (0.200 g).
points
One hundredth of a carat (0.01 ct.).
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karat
A unit of measure for the fineness of gold, abbreviated “K” or “Kt.”
durability
A gemstone’s ability to withstand wear, heat, and chemicals.
hardness
How well a gemstone resists scratches and abrasion.
toughness
How well a gemstone resists breaking and chipping.
stability
How well a diamond resists chemicals and temperature changes.
Ranking of the relative hardness of 10 minerals.
thermal shock
Damage caused by sudden, extreme temperature changes.
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