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Gemological Guidelines for Gemstone Durability in
Jewelry
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Gem Material
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Mohs Hardness
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Toughness
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Beryl
Aquamarine & others
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7 ½-8
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Good
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Use extra care if liquid inclusions or
feathers present.
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Emerald
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7 ½-8
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Poor to Good
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Avoid heat: may cause fracture or breakage. Polishing compound may get into
surface-breaking fractures.
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Coral
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3-4
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Fair to Good
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Avoid heat
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Corundum
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9
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Excellent except in highly twinned or
fractured stones
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|
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Avoid extreme heat: may alter
color. Polishing compound may
enter inclusions/fractures breaking the surface. Oiled or dyed stones: avoid solvents.
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Star Ruby & Sapphire
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9
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|
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Diamond
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10
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Good to exceptional
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Use cautions if stone
contains feathers of is included.
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Diamond, Colored
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10
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Food to exceptional
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Garnet
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7-7 ½ Damantoild:
6 ½ - 7
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Fair to good
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Ultrasonic: risky is liquid inclusions
present. Avoid thermal shock.
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Iolite
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7 – 7 ½
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Fair
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Normal cautions.
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Ivory
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2 ½ - 2 ¾
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|
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Avoid solvents. Clean with cloth
dampened in ethylated spirits.
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Jade
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6 ½ - 7
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Exceptional
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|
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Treated: avoid strong solvents
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Lapis Lazuli
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5-6
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Fair
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Dyed: avoid acetone and other solvents.
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Opal
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5-6 ½
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Poor to Fair
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Heat turns stone white or brown and
destroys play of color. Thermal
shock casues cracking, crazing, fracture
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Pearl
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2 ½ - 4
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Usually good but variable
|
|
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Avoid heat; causes cracking, may cause
pearl to turn brown, burn or split.
Attacked by all acids
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Peridot
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6 ½ - 7
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Fair to good
|
|
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Normal cautions
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Quart
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7
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Good
|
|
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Avoid thermal shock
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Topaz
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8
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Poor
|
|
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Avoid thermal shock
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Tourmaline
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7 – 7 ½
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Fair
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Avoid thermal shock
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Turquoise
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5 – 6
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Poor to good
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Avoid heat and chemicals. Ultrasonic solution may discolor.
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From Gem and Gemology
Summer Issue 1987
GIA Publications
Cleaning:
The reaction
of a stone to either cleaning ultrasonic or steaming will
vary depending on the inclusions in the stone, the solution used in
the ultrasonic, and the amount of time the stone remains in the ultrasonic,
as well as on the procedure used in steaming. All stones are at risk of thermal shock
if taken from the steamer and placed directly in the ultrasonic or water
before they have sufficiently cooled.
Caution is advised regarding solvents and other chemicals, including
ammonia, which is common constituent of most household cleaners. Boiling is not recommended for any stone
except diamond and only for diamond when absolutely necessary and proper
procedures are followed.
Because
IONIC CLEANING is done at room temperature and without cavitation
it has been found to be SAFE for all stones. No heat or sound waves
are used in the ionic process; simply
bubbles releasing tarnish and oxidation from metal as stones are
bathed in the Gem Sparkle solution.
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