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Postage stamps dedicated to Sapphire!
image location - stampmin.home.att.net |
Sapphire under a microscope!
image location - microscopy.fsu.edu |
Pure Corundum is colorless, but trace amounts of other metallic elements substituting for
the aluminum atoms in the aluminum oxide matrix produce the full range of colors. Red corundum
is known as ruby, while all non-red varieties of corundum are known as sapphires. Most people
think of sapphires as being blue, but colorless, black, violet, green, yellow, orange, pink
and everything in-between are common. Iron, chromium, vanadium, cobalt and nickel are
responsible for many of the sapphire variants. Rich, vibrant, transparent blue is the most
rare and desirable variation, and will often be priced hundreds or even thousands of dollars
per carat for better specimens. Sapphires are normally heated, but are often treated with
various radiation, diffusion, or other treatment methods to improve the color and clarity.
Certifiably untreated stones will often bring a higher price than those that have been
treated. Corundum often includes minute rutile inclusions, which if sufficiently
concentrated, will cause an asterism, or a six-rayed star. The largest sapphire crystal on
record is a 355-pound specimen on display in Johannesburg, South Africa.
Corundum is one of the most abundant minerals found and at one time was the most common
abrasive used to make sandpaper. Gem quality stones are normally found in gravel deposits
from weathered metamorphic or igneous formations that are rich in aluminum and short on
silica. The most famous and prolific production has historically been from Burma, Thailand,
India and Sri Lanka, however most modern day sapphires originate in Australia and Tanzania
and Kenya in Africa. Other important sources include Pakistan, Cambodia, Malawi, Colombia,
Brazil, Nigeria, China, Zimbabwe, Madagascar and Montana in the United States.
| Composition | Al2O3 | Class | oxide |
| Specific gravity | 3.98 to 4.10 | Refractive Index | 1.76 to 1.78 |
| Birefringence | weak 0.007 to 0.010 | Pleochroism | very distinct |
| Cleavage | none | Fracture | conchoidal, brittle |
| Luster | adamantine to vitreous | Transparency | transparent to translucent |
| Streak | white | Fluorescence | |
| Crystal system | hexagonal-rhombohedral | Twinning | common |
| Hardness | 9.0 | Dispersion | .018 |
| Color | blue, pink, green, yellow, violet, purple, orange, brown, white, gray, black and colorless. |
| Crystal habit | Commonly prismatic, rminated by basal pinacoids. Pyramidal and rhombohedral faces may be partly or entirely absent. Often occur as tapering hexagonal pyramids with a barrel-shaped form |
| Other |
The name corundum was derived either from the Sanskrit kurivinda or from the Indian name
for corundum kauruntaka. Sapphire is from the Latin word for blue sapphirus, which is also
thought to have been used in ancient times in referring to lapis lazuli. It is among the
oldest gems known to man, dating back to at least the 7th Century BC when it was mined in
India and what is now Sri Lanka.
The sky is just a gigantic blue sapphire into which the earth is embedded was the belief
cherished in ancient times. Sapphire symbolizes loyalty, truth and faithfulness, while at the
same time expressing love and yearning. It was said to bring divine favor, to make peace
between enemies and to protect against envy, fraud, poison and sorcery. The wearing of a
sapphire signified generosity, good manners, wisdom and noble thoughts. Star sapphires were
believed to serve as protection against witchcraft. Tradition holds that Moses received the
Ten Commandments on tablets of beautiful blue sapphire and it was one of the twelve stones in
the breastplate of Aaron.
