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About Sapphires
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| Ruby and sapphire
are both corundum but sapphires are corundum of all colors except
red. Red corundum is called ruby. Although pure corundum is colorless, blue sapphire results from a combination of
titanium and iron oxides. The name sapphire comes from the Greek word
"sapphirus" for blue but sapphires come in many colors including black, purple,
violet, light |
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| blue, pink, yellow, orange,
green, and the rare orange-pink "padparadscha" sapphire. Padparadscha comes from
the Sinahalese word meaning "lotus color". Sapphires other than blue ones are
usually called "natural fancy-color sapphire". Red hues result from traces of
chromium. The greater the concentration of oxides, the deeper the color. Sapphire's enchanting colors
are just one reason for this gemstone's popularity. It's also extremely durable, having a
hardness of 9 on the Mohs scale. Sapphire has a
specific gravity of 4.00, a refractive index of 1.76 - 1.78, and birefringence of 0.008. |
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The refractive index
(RI), measured using a refractometer, is an indication of the amount light rays
are bent by a mineral. Birefringence is the
difference between the minimum and maximum RI. When birefringence is high, light
rays reflect off |
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| different parts of the back of
a stone causing an apparent doubling of the back facets when viewed through the front
facet. Most gems have a
crystalline structure. Crystals have planes of symmetry and are divided into seven
symmetry systems. The number of axes, their length, their angle to each other determine
the system to which a crystal belongs.
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| Sapphire is classified as
having a trigonal crystalline structure because
it has three planes of symmetry and four axes. Three axes are at 60 degrees to each other
in the same plane. The fourth axis is perpendicular and unequal in length to the other
three. The form of a sapphire's crystals
depends on the variety and locality. Sapphires may have an unveven or |
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| a conchoidal
fracture but no real cleavage. The amount of light reflected at the surface of a gemstone
is its luster and sapphires have a glassy (vitreous) luster as opposedto the waxy, greasy,
or resinous luster of other stones. Fibers
or fibrous cavities within a gem such as a sapphire reflect the light which
creates a star to appear within the stone. A six-ray star has |
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three sets of parallel fibers.
Skilled cutters can sometimes create a 12-ray star sapphire. Star sapphires are cut
as cabochon to create a star effect. |
For decades, the basaltic lava rocks and river sands and gravels of Burma, Thailand,
Pailin, Cambodia have been major sources of excellent quality gems. Other sources of sapphire are
Australia, Brazil, Kashmir, Kenya,
Malawi, Tanzania, Zimbabwe and Montana, USA.
Today, however, there is a new and important source of gem
quaity sapphires on the market -- Madagascar.
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image to enlarge
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Its sapphires are similar in appearance, quality, and material to
those from Sri Lanka. Generally they are indistinguishable from
Ceylon sapphires and are interchangeable in value. |
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image to enlarge
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image to enlarge
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Of all the buyers of gemstones in Africa, approximately 75% are Thais and
20% are Sri Lankans buying rough in Madagascar. Most of the rough
is brought back to
Thailand for processing. |
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click
image to enlarge
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If you are interested in
learning more
about Madagascar sapphires, see the cover story of the
November/December issue of "Colored Stone Magazine".
You'll find the story "Madagascar" on pages 18-22 which
features AJS Gems.
The myths, legends, beliefs,
superstitions, traditions and symbolism associated with sapphire have been numerous.
Sometimes called the "Gem |
| of Heaven", it's
reflection was long ago credited for the blue of the sky. To others it was a symbol of
truth, a poison antidote, protection from evil, and a cure for mental illness. Sapphire is now the birthstone for September but a
millenium ago it was the birthstone for April and a talisman for the sun sign Taurus (21
April to 21 May). |
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| It's the gemstone
for Thursday as well. Sapphire is frequently
part blue and the rest colorless. When this happens the cutter puts the clear
part near the front of the gem and the blue part in the back so the stone appears blue
when viewed from the front. Buy from a reliable source like AJS Gems.
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Importer & exporter of rough & polished gemstones for the wholesale gemstone industry, gem cutters, jewelers & gemstone collectors!
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