GIA Colored Stones
Exam terms exam
questions and answers
A natural, inorganic substance with a characteristic
chemical composition and usually characteristic
structure. - answer Mineral
A cutting style that combines brilliant-cut and step
cut facets. - answer Mixed cut
Tiny nicks and pits caused by wear and damage to
a gem's facet edges or culet. - answer Abrasions
A pattern of dark vertical lines or bands shown by
certain gems when viewed through a spectroscope.
- answer Absorption spectrum
The cloudy bluish white light in a moonstone,
caused by scattering of light. - answer
Adularescence
,Chalcedony with a curved or angular bands or
layers that differ in color and transparency . -
answer Agate
A mass of tiny, randomly oriented crystals. -
answer Aggregate
Common name for the Pinctada fucata oyster and
the natural or cultured pearls it produces. - answer
Akoya
A gem colored by trace elements in its crystal
structure. - answer Allochromatic
A deposit where gems are eroded from their source
rock, then transported away from their source and
further concentrated. - answer Alluvial deposit
Lacking a regular crystal structure. - answer
Amorphous
A crystalized form of calcium carbonate found in
nacre. - answer Aragonite
Two or more separate pieces of material joined to
form a unit. - answer Assembled stone
,Crossing of chatoyant bands, creating a star in the
dome of cabochon. - answer Asterism
The basic structural unit of all matter. - answer
Atom
A glittery effect caused by light reflecting from
small, flat inclusions within a gemstone. - answer
Aventurescence
An opal's bodycolor, independent of its play-of-
color. - answer Background color
A bead used as the core of a cultured pearl, usually
made from a freshwater mussel shell. - answer
Bead nucleus
A treatment that uses chemicals to lighten or
remove color. - answer Bleaching
Characteristic or irregularity confined to the
surface of a polished gemstone. - answer Blemish
, Trade term for a highly prized, vivid blue
adularescence displayed by the finest moonstone. -
answer Blue Sheen
A gemstone's basic color, determined by its
selective absorption of light. - answer Bodycolor
A crystal growth habit with a bumpy appearance
similar to a bunch of grapes. - answer Botryoidal
Thin layers of precious opal, cut to include matrix. -
answer Boulder opal
A cylindrical synthetic crystal produced by the
flame-fusion process. - answer Boule
Light that eventually returns to the eye after
entering a gem through the crown, reflecting off its
pavilion facets, and exiting back through the
crown. - answer Brilliance
Cutting style with triangular or kite-shaped facets
that radiate from the center toward girdle. -
answer Brilliant cut
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