GIA Colored Stones Exam 651-700 Flashcards
Heating wrapped opal until smoke or ash penetrates its surface to darken it and bring out its play_of_color is called ____________.
smoke treatment
Soaking an opal in a hot sugar solution and then in sulfuric acid to darken it and bring our its play_of_color is called ___________.
sugar treatment
Altering a gem’s appearance by applying backings; coatings or coloring agents like paint is called ___________.
surface modification
What are the most commonly heat treated gemstones?
corundum; zircon; topaz; tanzanite; aquamarine; amber
Heat treatment can alter color and create or eliminate ____________ and ___________.
phenomena; inclusions
Lattice diffusion with titanium produces what?
a shallow layer that can be removed with minor polishing.
Lattice diffusion with what element may penetrate the entire stone?
beryllium
Almost all emeralds on the market today are what?
fracture filled
Common irradiated gems include ____________.
topaz; tourmaline; cultured pearl
What is one of the oldest gem treatments?
dyeing
Commonly dyed gems include _______________.
cultured pearl; chalcedony; coral; lapis; lazuli
A characteristic or irregularity confined to the surface of a polished gemstone is called a ___________.
blemish
An angular; hollow space that resembles a mineral inclusion is called a ______________
negative crystal
A general term for a break in a stone is called a ____________.
feather
An inclusion with the most negative impact on a colored stone’s clarity would be located where?
under the table
Which colored stone clarity type are the gems usually eye_clean?
Type I
The highest clarity grade for colored stones is ___________.
eye_clean
The term “silk” describes _____________.
a group of fine needle_like inclusions
Fingerprints are considered what?
fractures
What gems would be classified as Type III?
emerald; red beryl; watermelon tourmaline
In which colored stone clarity grades do the definitions vary for each clarity type?
moderately included
What clarity characteristic would usually have the greatest impact on a gem’s marketability?
a large unhealed feather
Gems that are usually eye_clean include ___________.
spodumene; yellow beryl; aquamarine
Inclusions are important to gemologists because they do what?
help seperate natural from synthetic gems
Growth zoning in a colored stone is evidence of what?
crystal growth
Two factors that determine an inclusion’s impact on a gem’s value are __________ and___________.
crystal system and size
Tiny nicks and pits caused by wear and damage to a gem’s facet edges or culet is called an ___________.
abrasion
An opening that extends into a gem from the surface is called a ___________.
cavity
A damaged area of a gem; usually near a girdle is called a ____________.
chip
Any hazy or milky area that cannot be described as a feather; fingerprint; or group of included crystals or needles is called a ____________.
cloud
A long; thin inclusion that can be a solid crystal or a hollow tube that might be filled with liquid or gas is called a _____________.
needle
Minute inclusion enclosed within a gem; can occur singly or in groups called clouds is called a _____________.
pinpoint
Contrast between an inclusion and its host gem is called ___________.
relief
A group of fine needle_like inclusions is called ____________.
silk
What are the five factors that determine influence of clarity characteristics on marketability?
nature; size; number; position and relief
Most gems are __________.
minerals
To be a gem a mineral must be what?
beautiful; durable; rare
What is the number one stone by value imported into the US?
emerald
Lacking a crystal structure.
amorphous
The basic structural element of all matter.
atom
A substance that consists of atoms of only one kind.
chemical element
Regular; repeating internal arrangement of atoms in a material is called its ___________.
crystal structure
A broad gem category based on chemical compostition and crystal structure is called __________.
gem species
A subcategory of species; based on color; transparency or phenomenon is called a ___________.
gem variety
A family of gems from several closely related mineral species is called a ______________.
group
Composed of; or arising from; non_living matter is considered ________.
inorganic
A natural; inorganic substance with a characteristic chemical composition and usually characteristic structure is called a __________.
mineral
Produced by; or derived from; a living organism is called ____________.
organic
A natural material composed of masses of mineral crystals of one or more kinds is called a _________.
rock
A mineral that contains the elements silicon and oxygen is called a __________.
silicate
