GIA Colored Stones Exam 401-450 Flashcards
Artistic gem cuts that aren’t limited to specific proportions or shapes are called ____________ .
designer cuts
A wooden or metal stick that holds the preform during faceting is called a __________ .
dopstick
A device that holds the dopstick at precise angles to allow correct orientation during faceting and polishing is called a ________ .
faceting head
A free_form cut that can feature alternating curved an flat surfaces is called a __________ .
fantasy cut
The narrow section that forms the boundary between the crown and the pavilion; and functions as the gem’s setting edge id called the ______ .
girdle
The process of giving approximate shape to a gemstone or producing flat planes for polishing facets is called _____________ .
grinding
A design engraved into the surface of a gemstone is called an __________ .
Intaglio
A horizontal spinning metal disk used to grind or polish a gem’s facets is called a ____________ .
lap
A cutting style that combines brilliant_cut and step_cut facets is called a ____________ .
mixed cut
The lower part of a faceted gem below the girdle is called the ____________ .
pavillion
The final stage in gem cutting that produces the smoothest possible surface is called ___________ .
polishing
Rough ground to approximate shape of the finished stone; also; the act of producing this shape is called ___________ .
preform
The angles and relative measurements of a polished gem; and the relationships between them is called ____________ .
proportions
Dividing the gem rough into easily handled pieces and removing waste areas is called _____________ .
sawing
A cutting style with mainly square and rectangular facets arranged in concentric rows is called a ___________ .
step cut
The arrangement of a stone facets is called the __________ .
style
The precision and balance of the corresponding parts of a finished gem is called it’s __________ .
symmetry
The facet at the top of the crown; usually the largest facet on the stone is called the ___________ .
table facet
Which type of rough is usually faceted?
transparent
To retain as much weight as possible from rare; high_quality rough; cutters would most likely vary the __________ .
proportions
Translucent to opaque rough is often cut into what type of cut?
cabochon
A carved design that projects slightly from a flat or curved surface is called ____________ .
a cameo
Colored stones cut flat with shallow pavilions usually have areas of lower color intensity called _______ .
windows
A cutter can darken the color of a pale stone by cutting a ___________ .
deep pavilion
To judge brilliance; view the stone in what direction?
face_up
What adds weight to a step cut?
excessive buldge
Colored stones that rate “fair” for brilliance have what percentage?
between 25 and 40 percent brilliance
The pattern of dark vertical lines or bands shown by certain gems when viewed through a spectroscope is called ______________ .
absorption spectrum
Which element does chromium substitute for that causes ruby’s red?
aluminum
A gem colored by the element that is part of its basic chemistry is called ______________ .
idiochromatic
Which element causes the color of both almandite and peridot?
iron
The process where electrons that selectively absorb light are passed back and forth between neighboring ions is known as ______________ .
intervalance charge transfer
Which components of a transition element’s atoms can produce color in gems?
electrons
Which element causes the finest reds and greens in gemstones?
chromium
Which transition element causes a greater variety of gem colors than any other?
iron
In many blue sapphires; the intervalence charge transfer that causes the color is between what two elements?
iron and titanium
When a gem’s crystal structure splits light into two rays that each travel at a slightly different speed and direction; it’s called ____________ .
double refraction
What is the only type of gem that can show pleochroism?
doubly refractive
Which gem can show three pleochroic colors?
andalusite; kyanite; tanzanite; iolite
What phenomenon shows a broad color flash?
labradorescence
Adularescence is caused by what?
A scattering of light as in moonstone
The best_known and most valuable chatoyant gem is cat’s_eye ____________ .
chrysoberyl
The cloudy bluish white light in a moonstone; caused by scattering of light.
adularescence
A gem colored by trace elements in its crystal structure.
allochromatic
Crossing of chatoyant bands; creating a star in the dome of a cabochon.
asterism
A glittery effect caused by light reflecting from small flat inclusions within a gemstone.
aventurescence
A small defect in the atomic structure of a material that can absorb light and give rise to a color.
color center
A special kind of interference phenomenon that breaks up white light and give rise to a color.
diffraction
Emission of visible light by a material when it’s stimulated by ultraviolet light.
fluorescence
A gem colored by an element that is an essential part of its chemical composition.
idiochromatic
