Gemstone/Origin
Description
Treatment
Effects
Care
Cleaning
Amethyst
(quartz) ⁄ Natural
Purple through bluish purple
Heat treatment
Lightens the color of very
dark amethyst; removes
smoky component of color
None
Ultrasonic: Usually safe
Steamer: Risky
Warm Soapy Water: Safe
Aquamarine
(beryl) ⁄ Natural
Greenish blue through
blue-green
Heat treatment
Produces blue from green,
iron–colored material
None
Ultrasonic: Usually safe, unless stone
contains feathers or liquid inclusions
Steamer: Usually safe, unless stone
contains feathers or liquid inclusions
Warm Soapy Water: Safe
Black Cultured Pearl
⁄ Organic
Contains body colors of
black, dark gray, or dark
tones of blue, purple, green,
or bronze
Irradiation
To produce "black" pearls
(also gray or blue gray) from
bleached pearls
Wipe with very soft cloth after
each wearing
Ultrasonic: Never
Steamer: Never
Warm Soapy Water: Safe for more
thorough cleaning (if strung, be sure
string is completely dry before washing)
Blue Quartz ⁄ Lab Created
Medium sky blue
       
Blue Topaz ⁄ Natural
Very slightly greenish blue to
greenish blue
Irradiation
Produces a blue color in
irradiated stones
Avoid heat and prolonged
exposure to strong light; if
radioactive (rare), avoid
handling and wear
Ultrasonic: Never
Steamer: Never
Warm Soapy Water: Safe
Citrine
(quartz)
⁄ Natural
Yellow through orange
Heat treatment
Produces citrine from
amethyst
Avoid steam
Ultrasonic: Usually safe
Steamer: Risky
Warm Soapy Water: Safe
Created Ruby (synthetic
corundum)
⁄ Lab Created
Very strong orangy red
Quench cracking (heating
and then plunging it into cold
water)
Produces cracks which
imitate natural breaks and
fingerprint inclusions
Avoid rough wear
Ultrasonic: Usually safe, but never for
oiled stones
Steamer: Usually safe, but never for oiled
stones
Warm Soapy Water: Safe, but avoid
strong detergents and vigorous
scrubbing on oiled stones
Cubic Zirconia
(synthetic)
⁄ Lab Created
Colorless
None
  None
Ultrasonic: Safe
Steamer: Safe
Warm Soapy Water: Safe
Cultured Pearl
⁄ Organic
Translucent to opaque
• Bleaching
• Dyeing
•Bleach dark spots of
conchiolin that show
through the nacre
• To alter the body color or
hide colored blemishes
Wipe with very soft cloth after
each wearing
Ultrasonic: Never
Steamer: Never
Warm Soapy Water: Safe for more
thorough cleaning (if strung, be sure
string is completely dry before washing)
Emerald
(beryl)
⁄ Natural
Very strongly bluish green
through green
Oiling (oil may contain green
dye)
Hides flaws, improves
transparency, may deepen
color
Keep away from strong
solvents, heat, and
ultrasonic cleaners
Ultrasonic: Never
Steamer: Never
Warm Soapy Water: Generally safe, but
avoid strong detergents and vigorous
scrubbing on oiled stones
Garnet
(pyrope)
⁄ Natural
Red through slightly purplish
red
None known
  None
Ultrasonic: Usually safe
Steamer: Risky
Warm Soapy Water: Safe
Iolite ⁄ Natural
Violet–blue through slightly
violet–blue
None known
  None
Ultrasonic: Risky
Steamer: Risky
Warm Soapy Water: Safe
Mother of Pearl
(shell)
⁄ Organic
Translucent to opaque
Dyeing
To produce a variety of colors
Avoid solvents and
prolonged exposure to
strong light
Ultrasonic: Risky
Steamer: Risky
Warm Soapy Water: Safe
Mount St. Helens ⁄ Lab
Created
Deep, clean bluish green
       
Mystic Fire Topaz ⁄ Natural
Greenish
Coated
Changes clear topaz to color
Normal
Ultrasonic: Unsafe
Steamer: Unsafe
Warm Soapy Water: Safe
Safe
Onyx
(chalcedony)
⁄ Natural
Solid black color
Dyeing
Chalcedony is dyed to
practically all colors for
various uses; the bands in
agate and onyx accept dye
differently so that a green
dye, for example, may impart
color to some layers and
leave others white
None
Ultrasonic: Usually safe
Steamer: Usually safe
Warm Soapy Water: Safe
Peridot ⁄ Natural
Yellowish green through
greenish yellow
No commercial treatments
known
  None
Ultrasonic: Risky
Steamer: Never
Warm Soapy Water: Safe
Pink Sapphire
(corundum)
⁄ Natural
Red through purple
Coating with a thin film
Creates, deepens, or
changes the color of a
sapphire
Avoid abrasions
Ultrasonic: Usually safe
Steamer: Usually safe
Warm Soapy Water: Safe
Pink Tourmaline ⁄ Natural
Red–orange through
reddish purple
Irradiation
Produces a deep pink to red
to deep purple from very
light pink, green, blue, or
colorless
None
Ultrasonic: Risky
Steamer: Risky
Warm Soapy Water: Safe
Rhodolite Garnet ⁄ Natural
Slightly purplish red through
reddish purple
None known
  None
Ultrasonic: Usually safe
Steamer: Never
Warm Soapy Water: Safe
Ruby
(corundum)
⁄ Natural
Orange-red through strongly
purplish red
Heat treatment
Removes purple or
brownish color component
None
Ultrasonic: Usually safe, but never for
oiled stones
Steamer: Usually safe, but never for oiled
stones
Warm Soapy Water: Safe, but avoid
strong detergents and vigorous
scrubbing on oiled stones
Sapphire
(corundum)
⁄ Natural
Violet–blue through
greenish blue
Heat treatment
Produces blue sapphire
from milky "gueda" sapphire
None
Ultrasonic: Usually safe
Steamer: Usually safe
Warm Soapy Water: Safe
Tanvorite ⁄ Lab Created
Deep, clean bluish⁄purple
       
Tanzanite
(zoisite)
⁄ Natural
Bluish purple and violet
through blue
Heat treatment
Produces tanzanite colors in
certain crystals with initially
brownish colors
None
Ultrasonic: Never
Steamer: Never
Warm Soapy Water: Safe
Safe
Information Source: Gem Reference Guide. Gemological Institute of America, 1995.