GIA Colored Stones 2023 Actual Questions and Answers
100% Verified
Mineral
A natural, inorganic substance with a characteristic chemical composition and usually
characteristic structure.
Mixed cut
A cutting style that combines brilliant-cut and step cut facets.
Abrasions
Tiny nicks and pits caused by wear and damage to a gem's facet edges or culet.
Absorption spectrum
A pattern of dark vertical lines or bands shown by certain gems when viewed through a
spectroscope.
Adularescence
The cloudy bluish white light in a moonstone, caused by scattering of light.
Agate
Chalcedony with a curved or angular bands or layers that differ in color and
transparency .
Aggregate
A mass of tiny, randomly oriented crystals.
Akoya
Common name for the Pinctada fucata oyster and the natural or cultured pearls it
produces.
Allochromatic
A gem colored by trace elements in its crystal structure.
Alluvial deposit
A deposit where gems are eroded from their source rock, then transported away from
their source and further concentrated.
Amorphous
Lacking a regular crystal structure.
Aragonite
A crystalized form of calcium carbonate found in nacre.
Assembled stone
Two or more separate pieces of material joined to form a unit.
Asterism
Crossing of chatoyant bands, creating a star in the dome of cabochon.
Atom
The basic structural unit of all matter.
Aventurescence
A glittery effect caused by light reflecting from small, flat inclusions within a gemstone.
Background color
An opal's bodycolor, independent of its play-of-color.
Bead nucleus
A bead used as the core of a cultured pearl, usually made from a freshwater mussel
shell.
,Bleaching
A treatment that uses chemicals to lighten or remove color.
Blemish
Characteristic or irregularity confined to the surface of a polished gemstone.
Blue Sheen
Trade term for a highly prized, vivid blue adularescence displayed by the finest
moonstone.
Bodycolor
A gemstone's basic color, determined by its selective absorption of light.
Botryoidal
A crystal growth habit with a bumpy appearance similar to a bunch of grapes.
Boulder opal
Thin layers of precious opal, cut to include matrix.
Boule
A cylindrical synthetic crystal produced by the flame-fusion process.
Brilliance
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.
Brilliant cut
Cutting style with triangular or kite-shaped facets that radiate from the center toward
girdle.
Cabochon
A smoothly rounded polished gem with a domed top and a flat or curved base.
Calcareous concretion
A non-nacreous natural "pearl".
Calibrated sizes
Gemstone sizes cut to fit standard mountings.
Cameo
A gem carving style in which the design often a women's profile, projects slightly from a
flat or curved surface.
Cavity
An opening that extends into a gem from the surface.
Centipedes
Tiny tension cracks in a moonstone that interfere with adularescence and reduce value.
Ceramic process
A process in which ground powder is heated, sometimes under pressure, to produce a
fine-grained solid material.
Certificate of origin
A document that indicates a stone's geographic origin, based on its inclusions and trace
element chemistry.
Chalcedony
A cryptocrystalline quartz aggregate.
Charge transfer
A process where the electrons that selectively absorb light are passed back and forth
between neighboring impurity ions.
Chatoyancy
,Bands of light in certain gems, caused by reflection of light from many parallel, needle-
like inclusions or hollow tubes.
Chemical composition
Kinds and relative quantities of atoms that make up a material.
Chemical element
A substance that consists of atoms of only one kind.
Chip
A damaged area on a gem, usually near the girdle.
Chrome tourmaline
Trade term for a vibrant green tourmaline that's colored by traces of vanadium,
chromium, or both.
Circled pearl
A pearl with one or more grooved or ridged rings all the way around it.
Cleavage
A smooth, flat break in a gemstone parallel to planes of atomic weakness, caused by
weak or fewer bonds between atoms or both.
Cloud
Any hazy or milky area that cannot be described as a feather, fingerprint, or group of
included crystals or needles.
Cobbing
Removing heavily included sections from a gemstone rough by carefully tapping it with
a small hammer.
Color center
A small defect in the atomic structure of a material that absorb light and give rise to a
color.
Color Change
A distinct change in gem color under different types of lighting.
Color range
The selection of colors in which a gemstone occurs.
Color zoning
Areas of different color in a gem, caused by variations in growth conditions.
Colorless impregnation
Filling of pores or other openings with melted wax, resin, polymer, or plastic to improve
appearance and stability.
Commercial market
Market sector where average-quality gemstones are used in mass-market jewelry.
Conchiolin
The organic "glue" in nacre that holds aragonite platelets together.
Conchoidal fracture
A curved and ridged fracture in a gemstone, extending from the surface inward.
Consignment
A selection of goods loaned to a dealer by another wholesaler or gem cutter.
Contact metamorphism
Localized changes caused by an igneous intrusion that takes place where the magma
meets the surrounding rock. New minerals may form due to temperature changes or
introduction of fluids from the magma.
, Core
The earth's innermost layer.
Crazing
The network of tiny fractures that develop when opal loses moisture.
Crown
Top part of the gem above the girdle.
Crown-height to pavilion-depth ratio
The relationship of the height of a gem's crown to the depth of its pavilion, judged by
viewing its profile,
Crust
The surface and outermost later of the earth.
Cryptocystalline
An aggregate made up of individual crystals detectable only under very high
magnification.
Crystal structure
Regular, repeating internal arrangement of atoms in a material.
Cultured blister pearl
A cultured pearl grown around a nucleus glued under the mantle tissue inside a
mollusk's shell.
Cultured pearl
A pearl formed as the result of human intervention in the formation process.
Custom-made jewelry
A unique piece designed and created for a particular customer, often around specially
chosen stones.
Cut
A gem dealer's term for a random sample from a parcel of gemstones, often used to
assess the parcel's overall quality.
Cutter
A manufacturer who produces faceted stones, cabochons, or carvings.
Cutting center
A city, region, or country with a large number of gemstone manufacturers.
Density
How heavy an object is in relation to its size.
Designer cuts
Artistic gem cuts that aren't limited to specific proportions or shapes.
Dhun
Smoky corundum that turns blue when treated.
Diffraction
A special kind of interference phenomenon that breaks up white light into spectral hues.
Disclosure
Clearly and accurately informing customer about the nature of the goods they buy.
Dopstick
Wooden or metal stick that holds the preform during faceting.
Double refraction
When a gem's crystal structure splits light into two rays that each travel at a slightly
different speed and direction.
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Mineral
A natural, inorganic substance with a characteristic chemical composition and usually
characteristic structure.
Mixed cut
A cutting style that combines brilliant-cut and step cut facets.
Abrasions
Tiny nicks and pits caused by wear and damage to a gem's facet edges or culet.
Absorption spectrum
A pattern of dark vertical lines or bands shown by certain gems when viewed through a
spectroscope.
Adularescence
The cloudy bluish white light in a moonstone, caused by scattering of light.
Agate
Chalcedony with a curved or angular bands or layers that differ in color and
transparency .
Aggregate
A mass of tiny, randomly oriented crystals.
Akoya
Common name for the Pinctada fucata oyster and the natural or cultured pearls it
produces.
Allochromatic
A gem colored by trace elements in its crystal structure.
Alluvial deposit
A deposit where gems are eroded from their source rock, then transported away from
their source and further concentrated.
Amorphous
Lacking a regular crystal structure.
Aragonite
A crystalized form of calcium carbonate found in nacre.
Assembled stone
Two or more separate pieces of material joined to form a unit.
Asterism
Crossing of chatoyant bands, creating a star in the dome of cabochon.
Atom
The basic structural unit of all matter.
Aventurescence
A glittery effect caused by light reflecting from small, flat inclusions within a gemstone.
Background color
An opal's bodycolor, independent of its play-of-color.
Bead nucleus
A bead used as the core of a cultured pearl, usually made from a freshwater mussel
shell.
,Bleaching
A treatment that uses chemicals to lighten or remove color.
Blemish
Characteristic or irregularity confined to the surface of a polished gemstone.
Blue Sheen
Trade term for a highly prized, vivid blue adularescence displayed by the finest
moonstone.
Bodycolor
A gemstone's basic color, determined by its selective absorption of light.
Botryoidal
A crystal growth habit with a bumpy appearance similar to a bunch of grapes.
Boulder opal
Thin layers of precious opal, cut to include matrix.
Boule
A cylindrical synthetic crystal produced by the flame-fusion process.
Brilliance
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.
Brilliant cut
Cutting style with triangular or kite-shaped facets that radiate from the center toward
girdle.
Cabochon
A smoothly rounded polished gem with a domed top and a flat or curved base.
Calcareous concretion
A non-nacreous natural "pearl".
Calibrated sizes
Gemstone sizes cut to fit standard mountings.
Cameo
A gem carving style in which the design often a women's profile, projects slightly from a
flat or curved surface.
Cavity
An opening that extends into a gem from the surface.
Centipedes
Tiny tension cracks in a moonstone that interfere with adularescence and reduce value.
Ceramic process
A process in which ground powder is heated, sometimes under pressure, to produce a
fine-grained solid material.
Certificate of origin
A document that indicates a stone's geographic origin, based on its inclusions and trace
element chemistry.
Chalcedony
A cryptocrystalline quartz aggregate.
Charge transfer
A process where the electrons that selectively absorb light are passed back and forth
between neighboring impurity ions.
Chatoyancy
,Bands of light in certain gems, caused by reflection of light from many parallel, needle-
like inclusions or hollow tubes.
Chemical composition
Kinds and relative quantities of atoms that make up a material.
Chemical element
A substance that consists of atoms of only one kind.
Chip
A damaged area on a gem, usually near the girdle.
Chrome tourmaline
Trade term for a vibrant green tourmaline that's colored by traces of vanadium,
chromium, or both.
Circled pearl
A pearl with one or more grooved or ridged rings all the way around it.
Cleavage
A smooth, flat break in a gemstone parallel to planes of atomic weakness, caused by
weak or fewer bonds between atoms or both.
Cloud
Any hazy or milky area that cannot be described as a feather, fingerprint, or group of
included crystals or needles.
Cobbing
Removing heavily included sections from a gemstone rough by carefully tapping it with
a small hammer.
Color center
A small defect in the atomic structure of a material that absorb light and give rise to a
color.
Color Change
A distinct change in gem color under different types of lighting.
Color range
The selection of colors in which a gemstone occurs.
Color zoning
Areas of different color in a gem, caused by variations in growth conditions.
Colorless impregnation
Filling of pores or other openings with melted wax, resin, polymer, or plastic to improve
appearance and stability.
Commercial market
Market sector where average-quality gemstones are used in mass-market jewelry.
Conchiolin
The organic "glue" in nacre that holds aragonite platelets together.
Conchoidal fracture
A curved and ridged fracture in a gemstone, extending from the surface inward.
Consignment
A selection of goods loaned to a dealer by another wholesaler or gem cutter.
Contact metamorphism
Localized changes caused by an igneous intrusion that takes place where the magma
meets the surrounding rock. New minerals may form due to temperature changes or
introduction of fluids from the magma.
, Core
The earth's innermost layer.
Crazing
The network of tiny fractures that develop when opal loses moisture.
Crown
Top part of the gem above the girdle.
Crown-height to pavilion-depth ratio
The relationship of the height of a gem's crown to the depth of its pavilion, judged by
viewing its profile,
Crust
The surface and outermost later of the earth.
Cryptocystalline
An aggregate made up of individual crystals detectable only under very high
magnification.
Crystal structure
Regular, repeating internal arrangement of atoms in a material.
Cultured blister pearl
A cultured pearl grown around a nucleus glued under the mantle tissue inside a
mollusk's shell.
Cultured pearl
A pearl formed as the result of human intervention in the formation process.
Custom-made jewelry
A unique piece designed and created for a particular customer, often around specially
chosen stones.
Cut
A gem dealer's term for a random sample from a parcel of gemstones, often used to
assess the parcel's overall quality.
Cutter
A manufacturer who produces faceted stones, cabochons, or carvings.
Cutting center
A city, region, or country with a large number of gemstone manufacturers.
Density
How heavy an object is in relation to its size.
Designer cuts
Artistic gem cuts that aren't limited to specific proportions or shapes.
Dhun
Smoky corundum that turns blue when treated.
Diffraction
A special kind of interference phenomenon that breaks up white light into spectral hues.
Disclosure
Clearly and accurately informing customer about the nature of the goods they buy.
Dopstick
Wooden or metal stick that holds the preform during faceting.
Double refraction
When a gem's crystal structure splits light into two rays that each travel at a slightly
different speed and direction.
