GIA Colored Stones Exam 251-300 Flashcards
Where is the most important historical ruby source?
Mogok; Myanmar
What city and country is the source for the majority of commercial_quality rubies.
Mong Hsu; Myanmar
In ancient Sanskrit ruby is called ratnaraj which means ____________ .
king of precious stones
The most valuable tone and saturation for ruby are __________ and __________ .
medium to medium dark tone; vivid saturation
Corundum can form only in an enviroment that is low in what element?
Silicon
Rubies that come from marble deposits are typically low in ___________ .
Iron
Ruby that originate in Thailand Cambodia and Madagascar are associated with what type of deposits?
alkali_basalt
What is the result from heat treating Mong Hsu rubies?
Eliminates dark centers or cores
The worlds largest corundum marketing center is located in what country?
Thailand
Switzerland exports rubies that are primarily ________ .
high_end
What location has supplied the world with most commercial_quality rubies since 1991?
Mong Hsu
The major source for rubies in the 1980’s was what country?
Thailand
Compared to rubies from Myanmar; most Thai rubies tend to be ___________ .
darker
Rubies from Pailin; Cambodia are similar to those from what country?
Thailand
Vietnamese rubies originate in what type of deposit?
marble
Where are the Penny Lane and John Saul mines located?
Kenya
Newly discovered ruby deposits at Vatomandry and Andilamena are in what country?
Madagascar
What three trace elements in differing amounts and combinations cause most fancy sapphire colors?
iron; titanium; chromium
What type of fancy sapphire has the highest per_carat value.
padparadschas
Other than padparadschas; what color fancy sapphire also commands top prices?
fine pink
What colors can be created by heating purple sapphires?
pink or red
What location has seen an increase in yellow and orange sapphires?
East Africa
An inexpensive natural substitute for diamond is a __________ .
colorless sapphire
What is the typical corundum color change?
daylight / blue or violet; incandescent / violetish purple to strongly reddish purple
What trace element causes sapphire’s color change?
Vanadium
The stars in the finest star corundums show these three characteristics ___________; ___________ and __________.
distinct; centered; uniform
The finest star corundum has a body color that provides ___________to the __________ .
strong contrast; star
What is the most valued star corundum?
star ruby
All being equal; which costs LESS; star ruby or blue star sapphire.
blue star sapphires
What area is a significant corundum source that promises to be even more productive in the future?
East Africa
The name padparadscha means _____________ .
lotus flower
What is the trade name for intensely saturated; light to medium pinkish orange to orange_pink sapphires?
padparadscha
Color_change sapphire typically changes from blue or violet to ___________ .
reddish purple
The most common number of rays in a star corundum is __________ .
six
Asterism in black star sapphire is caused by _________ .
hematite
The best quality star corundum has what type of tranparency?
semi_transparent
Which is the most prized body color in star corundum?
red
What trace element causes the pink color of corundum?
chromium
Which fancy sapphire hue regularly commands top prices?
pink
Green sappire is _______ .
readily available
Which color star sapphire is usually cut shallow due to parting?
black
What country is the major source of black sapphire?
Australia
Fancy sapphires from Montana tend to be __________ .
light in tone
The first flame fusion star rubies were produced in what time period?
1940’s
Strongly saturated blue or violetish blue.
Tanzanite
Why must cutters balance tanzanite’s weight retention against the quality of face_up color?
Tanzanite’s strong plechroism
What treatment is used to bring out tanzanite’s more attractive blue and violet hues?
heat treatment
What country is the only commercial source of tanzanite?
Tanzania
What moderately priced commercial_quality stone (when available) is more marketable than commercial_quality tanzanite?
blue sapphire
What is the most convincing tanzanite imitation?
synthetic forsterite
