Quiz 14 (GI 14, CS21)
Gem-quality benitoite is mined only in the US state of
California
The most-prized chatoyant gem in the world is
Cats eye chrysoberyl
Blue topaz's DR nature separates it from SR synthetic spinel, and it's RI of what separates it from aquamarine?
1.61 to 1.62
Tourmaline's birefringence, strong dichroism, and RI of what readily distinguish it from corundum, tanzanite, and iolite?
1.62 to 1.64
When Alexandrite was discovered
1830
When was tanzanite first discovered?
1967
When did TanzaniteOne buy AFGEM and its assets?
2004
Tanzanite ranks what on the Mohs scale?
6 to 7
Iolite and andalusite rank what on the Mohs scale?
7 to 7.5
Alexandrite ranks what on the Mohs scale?
8.5
About what percent of tanzanite is heat treated?
95
What stone is the finest color change gem and the standard for which all other color change gems are judged
Alexandrite
Which gem was named after a Russian czar?
Alexandrite
A slightly greenish blue, faceted stone with a low RI of 1.572, a high RI of 1.580, and a uniaxial optic character would be identified as
Aquamarine
Which of the following would be most helpful for separating blue apatite from Paraíba tourmaline?
Birefringence
In iolite, the most valuable main face-up color is
Blue
What color is top-quality alexandrite in daylight?
Blueish green
Cutting tanzanite to emphasize which color usually wastes less of the rough?
Bluish Purple
Untreated tanzanite is typically
Brownish
The color change in alexandrite is caused by
Chromium
What was the old Victorian name for yellow Chrysoberl?
Chrysolite
What are the pleochroic colors for violet iolite?
Light violet, dark violet, and yellow-brown
Virtually any shade of blue in glass is caused by
Cobalt
What are the pleochroic colors for bluish iolite?
Colorless to yellow, blue-gray, and dark violet
Turquoise is colored by
Copper
What is an old Greek word for cat's-eye chrysoberyl that means ""wavelike form""?
Cymophane
Heat-treated blue zircon
Displays strong doubling
When was alexandrite found in Brazil?
Early 1980s
What makes chrysoberyl the most prized chatoyant gem?
Excellent hardness and durability combined with the sharpest cats eye
Which method is used to produce most synthetic blue sapphires?
Flame fusion
What are the pleochroic colors of alexandrite?
Green, orange, and purple-red
Almost all tanzanite is
Heat Treated
Tanzanite's distinctive trichroism and what make it easy to separate from natural or synthetic sapphire?
Lower RI
Which of the following tests can help you separate natural sapphire from synthetic sapphire and treated sapphire?
Magnification and immersion
What changes during alexandrite's color-change effect?
Hue
What is the trade name for gem quality cordierite?
Iolite
What causes iolite's violetish blue to violet color?
Iron
What proves that a blue spinel is natural?
Iron lines in spectrum
Iron lines in a blue spinels spectrum prove what?
Its natural
An opaque, dark violet-blue cabochon containing pyrite flecks, with an RI of 1.50 and a moderate yellowish green fluorescence under SWUV, would be identified as
Lapis Lazuli
Where was tanzanite discovered?
Merelani
The best way to separate sapphire from both tourmaline and tanzanite is by its
RI and Birefringence
When separating iolite from tanzanite, the most helpful characteristics are
RI and Pleo
Which of the following is most helpful for separating natural dark blue spinel from flux synthetic dark blue spinel?
Spectrum
What is a major source of Iolite, cat's-eye chrysoberyl, and alexandrite?
Sri Lanka
Many natural sapphires show distinctive iron absorption spectra consisting of
Strong bands in the blue
What is the most convincing tanzanite imitation to date?
Synthetic forsterite
Which of the following gems is the most economically important?
Tanzanite
Pectolite can resemble
Turquoise
Which of these man-made stones is a true synthetic?
Turquoise
A translucent to opaque pink zoisite, often streaked or mottled with gray or white, is called
Thulite
The name tanzanite was given to transparent blue zoisite by
Tiffany and co
What separates Iolite from gems of the same body color
Trichroism
Top-color iolite is
Untreated
Where was alexandrite first discovered?
Ural Mountains in Russia
""Mint chrysoberly"" is colored by
Vanadium
OTL RI, prominent doubling, and unique spectrum separate what gem from other transparent blue stones?
Zircon
Most translucent-to-opaque blue and violet gems are
aggregates of one or more minerals
A good way to distinguish turquoise from synthetic turquoise is to
carefully examine the stones under magnification
What causes the Cat's eye in chrysoberyl?
light reflecting from needle like inclusions in the gemstones
"Swiss lapis" is a misnomer for
opaque dyed blue chalcedony
Tanavyte is a trade name for
purple synthetic YAG
Tanzanite's best color is
strongly saturated blue or violetish blue
A fast way to determine if blue chalcedony is dyed or naturally colored is to
view it under the color filter