Assignment 13 - Sapphire Flashcards
What is blue sapphire’s most important value factor?
Color
What causes sapphire’s blue?
Iron and Titanium
How are sapphires sometimes described in the trade?
The trade term “Kashmir” refers to what many consider the finest blue sapphires.
What factors influence a cutter’s fashioning decisions?
Cutters must consider color zoning, a common sapphire characteristic.
What are sapphire’s typical clarity characteristics?
Blue sapphires typically have some inclusions, but they generally have better clarity than rubies. Blue sapphires with extremely high clarity are rare, and very valuable.
Some of the typical inclusions in sapphire are silk (rutile needles),
boehmite needles, included crystals, fingerprint inclusions, growth zoning, and color zoning.
How do treatments affect blue sapphire’s appearance?
It’s estimated that most blue sapphires are treated in some way. Heating and lattice diffusion are the most common treatments.
What are the challenges involved in determining a sapphire’s origin?
Because heat treatment alters inclusions, it’s difficult to rely on them for identification. And rough from various deposits can
look the same, making recognition based on appearance practically impossible.
What are some past and present sources of blue sapphire?
Current sources responsible for the bulk of commercial-quality blue sapphire include Madagascar, Australia, Sri Lanka, and Nigeria.
Although supplies from previously important sources like Thailand and Cambodia have dwindled, gems from these locations sometimes come back into circulation through private sales and auctions.
What role do synthetic and imitation blue sapphires play in the market?
Historically, the two materials most commonly used to imitate sapphire have been glass and synthetic spinel.
The availability of evenly colored kyanite has led to its use as an imitation, as it has the same color-causing iron-titanium mechanism as sapphire.
Tanzanite is also used in sapphire’s place, as the violetish component of its blue color can mimic sapphire’s rich appearance. Tanzanite is more readily available in larger sizes than sapphire.
Laboratories all over the world have produced synthetic sapphires. The most common method is flame fusion, which can produce synthetic sapphire and other synthetic gemstones quickly and inexpensively.
Minute inclusions can give Kashmir sapphires a(n)
A. light tone.
B. inky color.
C. very dark tone.
D. velvety appearance.
D. velvety appearance.
Blue sapphires that originate in basaltic rock generally have
A. low iron content.
B. high iron content.
C. high chromium content.
D. high manganese content.
B. high iron content.
Kashmir’s most important sapphire production period was from
A.
1789 to 1802.
B.
1840 to 1851.
C.
1881 to 1887.
D.
1901 to 1936.
C.
1881 to 1887.
Blue sapphire’s most common crystal habit is a(n)
A.
octahedron.
B.
twinned octahedron.
C.
long hexagonal prism.
D.
spindle-shaped hexagonal pyramid or bipyramid.
D.
spindle-shaped hexagonal pyramid or bipyramid.
Regions associated with basalt-related sapphire include Cambodia, Thailand, Nigeria, and
A.
Kashmir.
B.
Australia.
C.
Myanmar.
D.
Sri Lanka.
B.
Australia.
Most fine sapphires over 100 cts. come from
A.
Montana.
B.
Australia.
C.
Sri Lanka.
D.
Cambodia.
C.
Sri Lanka.
