GIA Colored Stones Exam terms
Questions and Answers Graded A+
Mineral - Correct answer-A natural, inorganic substance with a characteristic
chemical composition and usually characteristic structure.
Mixed cut - Correct answer-A cutting style that combines brilliant-cut and step cut
facets.
Abrasions - Correct answer-Tiny nicks and pits caused by wear and damage to a
gem's facet edges or culet.
Absorption spectrum - Correct answer-A pattern of dark vertical lines or bands
shown by certain gems when viewed through a spectroscope.
Adularescence - Correct answer-The cloudy bluish white light in a moonstone,
caused by scattering of light.
Agate - Correct answer-Chalcedony with a curved or angular bands or layers that
differ in color and transparency .
Aggregate - Correct answer-A mass of tiny, randomly oriented crystals.
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,Akoya - Correct answer-Common name for the Pinctada fucata oyster and the
natural or cultured pearls it produces.
Allochromatic - Correct answer-A gem colored by trace elements in its crystal
structure.
Alluvial deposit - Correct answer-A deposit where gems are eroded from their
source rock, then transported away from their source and further concentrated.
Amorphous - Correct answer-Lacking a regular crystal structure.
Aragonite - Correct answer-A crystalized form of calcium carbonate found in
nacre.
Assembled stone - Correct answer-Two or more separate pieces of material joined
to form a unit.
Asterism - Correct answer-Crossing of chatoyant bands, creating a star in the dome
of cabochon.
Atom - Correct answer-The basic structural unit of all matter.
Aventurescence - Correct answer-A glittery effect caused by light reflecting from
small, flat inclusions within a gemstone.
Background color - Correct answer-An opal's bodycolor, independent of its play-
of-color.
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,Bead nucleus - Correct answer-A bead used as the core of a cultured pearl, usually
made from a freshwater mussel shell.
Bleaching - Correct answer-A treatment that uses chemicals to lighten or remove
color.
Blemish - Correct answer-Characteristic or irregularity confined to the surface of a
polished gemstone.
Blue Sheen - Correct answer-Trade term for a highly prized, vivid blue
adularescence displayed by the finest moonstone.
Bodycolor - Correct answer-A gemstone's basic color, determined by its selective
absorption of light.
Botryoidal - Correct answer-A crystal growth habit with a bumpy appearance
similar to a bunch of grapes.
Boulder opal - Correct answer-Thin layers of precious opal, cut to include matrix.
Boule - Correct answer-A cylindrical synthetic crystal produced by the flame-
fusion process.
Brilliance - Correct answer-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.
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, Brilliant cut - Correct answer-Cutting style with triangular or kite-shaped facets
that radiate from the center toward girdle.
Cabochon - Correct answer-A smoothly rounded polished gem with a domed top
and a flat or curved base.
Calcareous concretion - Correct answer-A non-nacreous natural "pearl".
Calibrated sizes - Correct answer-Gemstone sizes cut to fit standard mountings.
Cameo - Correct answer-A gem carving style in which the design often a women's
profile, projects slightly from a flat or curved surface.
Cavity - Correct answer-An opening that extends into a gem from the surface.
Centipedes - Correct answer-Tiny tension cracks in a moonstone that interfere with
adularescence and reduce value.
Ceramic process - Correct answer-A process in which ground powder is heated,
sometimes under pressure, to produce a fine-grained solid material.
Certificate of origin - Correct answer-A document that indicates a stone's
geographic origin, based on its inclusions and trace element chemistry.
Chalcedony - Correct answer-A cryptocrystalline quartz aggregate.
©COPYRIGHT 2025, ALL RIGHTS RESERVED 4
Questions and Answers Graded A+
Mineral - Correct answer-A natural, inorganic substance with a characteristic
chemical composition and usually characteristic structure.
Mixed cut - Correct answer-A cutting style that combines brilliant-cut and step cut
facets.
Abrasions - Correct answer-Tiny nicks and pits caused by wear and damage to a
gem's facet edges or culet.
Absorption spectrum - Correct answer-A pattern of dark vertical lines or bands
shown by certain gems when viewed through a spectroscope.
Adularescence - Correct answer-The cloudy bluish white light in a moonstone,
caused by scattering of light.
Agate - Correct answer-Chalcedony with a curved or angular bands or layers that
differ in color and transparency .
Aggregate - Correct answer-A mass of tiny, randomly oriented crystals.
©COPYRIGHT 2025, ALL RIGHTS RESERVED 1
,Akoya - Correct answer-Common name for the Pinctada fucata oyster and the
natural or cultured pearls it produces.
Allochromatic - Correct answer-A gem colored by trace elements in its crystal
structure.
Alluvial deposit - Correct answer-A deposit where gems are eroded from their
source rock, then transported away from their source and further concentrated.
Amorphous - Correct answer-Lacking a regular crystal structure.
Aragonite - Correct answer-A crystalized form of calcium carbonate found in
nacre.
Assembled stone - Correct answer-Two or more separate pieces of material joined
to form a unit.
Asterism - Correct answer-Crossing of chatoyant bands, creating a star in the dome
of cabochon.
Atom - Correct answer-The basic structural unit of all matter.
Aventurescence - Correct answer-A glittery effect caused by light reflecting from
small, flat inclusions within a gemstone.
Background color - Correct answer-An opal's bodycolor, independent of its play-
of-color.
©COPYRIGHT 2025, ALL RIGHTS RESERVED 2
,Bead nucleus - Correct answer-A bead used as the core of a cultured pearl, usually
made from a freshwater mussel shell.
Bleaching - Correct answer-A treatment that uses chemicals to lighten or remove
color.
Blemish - Correct answer-Characteristic or irregularity confined to the surface of a
polished gemstone.
Blue Sheen - Correct answer-Trade term for a highly prized, vivid blue
adularescence displayed by the finest moonstone.
Bodycolor - Correct answer-A gemstone's basic color, determined by its selective
absorption of light.
Botryoidal - Correct answer-A crystal growth habit with a bumpy appearance
similar to a bunch of grapes.
Boulder opal - Correct answer-Thin layers of precious opal, cut to include matrix.
Boule - Correct answer-A cylindrical synthetic crystal produced by the flame-
fusion process.
Brilliance - Correct answer-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.
©COPYRIGHT 2025, ALL RIGHTS RESERVED 3
, Brilliant cut - Correct answer-Cutting style with triangular or kite-shaped facets
that radiate from the center toward girdle.
Cabochon - Correct answer-A smoothly rounded polished gem with a domed top
and a flat or curved base.
Calcareous concretion - Correct answer-A non-nacreous natural "pearl".
Calibrated sizes - Correct answer-Gemstone sizes cut to fit standard mountings.
Cameo - Correct answer-A gem carving style in which the design often a women's
profile, projects slightly from a flat or curved surface.
Cavity - Correct answer-An opening that extends into a gem from the surface.
Centipedes - Correct answer-Tiny tension cracks in a moonstone that interfere with
adularescence and reduce value.
Ceramic process - Correct answer-A process in which ground powder is heated,
sometimes under pressure, to produce a fine-grained solid material.
Certificate of origin - Correct answer-A document that indicates a stone's
geographic origin, based on its inclusions and trace element chemistry.
Chalcedony - Correct answer-A cryptocrystalline quartz aggregate.
©COPYRIGHT 2025, ALL RIGHTS RESERVED 4
