GIA Colored Stones Assignment
4 Questions and Answers
(Graded A)
color - ANSWER - This is the most important factor in determining a colored
gemstone's desirability, marketability, and value.
light - ANSWER - This is a form of energy that travels in waves.
selective absorption - ANSWER - Most gem color is caused by...
chemical composition and crystal structure - ANSWER - Selective absorption is
influenced by... (2)
visible light - ANSWER - Some colored gems can be identified by the way they
absorb...
trasition element - ANSWER - Because of differences in crystal structure, the same
____________________ can cause different colors in different gems.
chromium - ANSWER - What causes the most desirable red and green gem colors?
iron - ANSWER - What transition element causes a greater variety of gem colors
than any other transition element?
charge transfer - ANSWER - What is responsible for most blue and yellow gem
colors?
double refraction - ANSWER - When a gem's crystal structure splits light into two
rays that each travel at a slightly different speed and direction.
, fluorescence - ANSWER - Emission of visible light by a material when it's stimulated
by ultraviolet radiation.
idiochromatic - ANSWER - A gem colored by an element that is an essential part of
its chemical composition.
interference - ANSWER - Interaction of two light rays traveling in the same path.
treatment - ANSWER - What can alter or initiate some color-causing charge transfer
reactions?
charge transfer - ANSWER - A process where the electrons that selectively absorb
light are passed back and forth between neighboring impurity ions.
chatoyancy - ANSWER - Bands of light in certain gems, caused by reflection of light
from many parallel, needle-like inclusions or hollow tubes.
color center - ANSWER - A small defect in the atomic structure of a material that can
absorb light and give rise to a color.
radiation - ANSWER - Without exposure to natural or artificial ____________, color
centers can't cause color in gems.
doubly refractive - ANSWER - Only _________________ gems can be pleochroic.
interference - ANSWER - What produces either darkness of the brightening of one or
more colors?
silica spheres - ANSWER - Opal's play-of-color is produced by the interaction of light
with the gem's microscopic internal structure of stacked ________________.
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