| Many people think all sapphires are
blue. But sapphires are actually corundum that are any color
except red. Red varieties are called rubies. Sapphires range
in color from violet--the most difficult to distinguish from a
ruby -- to blue, green, yellow, orange, pink, and purple. The
general term for any color except blue is "Fancy."
The GIA is shying away from using "place" names in
describing color. But you can still use fanciful language when
selling the beauty of color. For example, the term
"padparadscha" ("pad" for short), meaning
"lotus color," is used to describe sapphires having
a rare pinkish-orange color. The most desired sapphire color
is pure cornflower (not cauliflower) blue. Small differences
in any of the color components--hue, tone, and saturation--can
have an important impact on value.
Probably the most important enhancement besides that
designed to improve color is that used to improve clarity.
Controlled heating and cooling can dissolve the slender rutile
needles (called silk) right into the crystal structure to
improve the clarity. Although large sapphires are rare, the
Smithsonian has the Logan sapphire--a 423 carat blue stone
from Sri Lanka.
The most important sapphire sources are Kashmir, Sri Lanka,
Thailand, Australia, and the Yogo Gulch in Montana. Other
sources include Burma, Kampuchea (Cambodia), Kenya, and
Tanzania.
Kashmir is the quintessential sapphire source! Blue
sapphire from Kashmir has always been very highly regarded
because of its superb cornflower blue color. The deposits were
located in 1881. Almost all Kashmir sapphires show zoning, and
this is one of the ways in which they can be identified. The
zoning is associated with very small layers of liquid
inclusions that give the velvety or sleepy appearance. The
Kashmir mines have not been operating, at least officially,
since 1983 and any crystals recovered were found by the
indigenous population who were forbidden to engage in mining
or in gem trading.
Gem quality sapphire is found in many parts of Queensland,
Australia but the main deposit is at Anakie. Sapphires
occurring in alluvial deposits were first discovered in 1870.
Colors include deep blue, green, opaque black, bronze and
yellow. Increased heating of Australian sapphire, in Thailand,
has reduced the volume of available inky-black Australian
sapphire. Thailand is today's leading source of sapphire. But
mining is not the reason. Instead, heating accounts for the
large volume of stones sold. The Thai have developed elaborate
procedures for "lightening Australian and darkening Sri
Lankan" sapphires. Costs for the rough, mining, and
cutting all fall behind the cost of the fuel needed to
maintain the ovens used to "cook" sapphire. Black
star sapphire is mined principally in Thailand. |
