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GEMSTONE PROPERTIES - Specific Gravity, Hardness, Refractive Index
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ENHANCEMENT: Any traditional process other than cutting and polishing that improves
the appearance (color/clarity/phenomena), durability or availability of a gemstone.
A gemstone enhancement is considered permanent as long as it does not change in
appearance (color and/or clarity) under normal wear, cutting repair, cleaning or
display conditions.
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Those which are not enhanced.
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N
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The "N" symbol appears on the chart only for natural stones which are not currently
known to be enhanced (Alexandrite, Garnet, etc.), however, the "N" symbol can also be
used for other natural gemstones in the event that a gemstone has received no
enhancement. That gemstone must be accompanied by a commercial document, such as, an
invoice, memorandum and/or a laboratory report to support the fact that the gemstone
is not enhanced.
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Those which are not normally enhanced.
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E
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The "E" symbol indicates that the gemstone has undergone its traditional enhancement
process. The type of enhancement process covered by this symbol is indicated on the
following chart. For example: The "E" designation for Aquamarine means only the
enhancement that is describes in the chart, i.e. thermal enhancement. In the case of
Emerald, the "E" designation refers to the penetration of colorless oil, wax
and resins into fissures to improve appearance as the traditional part of the Emerald
enhancement process.
Since many enhancements are difficult or impractical to prove definitively, unless
otherwise indicated, to assume that such traditional enhancement has been done to that
particular gemstone.
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SYMBOLS FOR SPECIFIC FORMS OF ENHANCEMENTS:
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B
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Bleaching: The use of heat, light and/or other agents to lighten or remove a
gemstone's color.
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C
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Coating: The use of such surface enhancements as lacquering, enameling, inking, foiling
or sputtering of films to improve appearance, provide color or add other special
effects.
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D
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Dyeing: The introduction of coloring matter into a gemstone to give it new color,
intensify present color or improve color uniformity.
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F
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Filling: The filling of surface breaking cavities or fissures with colorless
glass, plastic, solidified borax or similar substances, which are visible under
properly illuminated 10X magnification. This process will improve durability,
appearance and/or add weight.
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H
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Heating: The use of heat to affect desired alteration of color, and/or phenomena.
(Residue of foreign substances in open fissures is not visible under properly
illuminated 10X magnification.)
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HP
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Heating and Pressure: The use of heat and pressure combines to affect desired
alterations of color and/or clarity.
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I
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Impregnation: The impregnation of a porous gemstone with a colorless agent
(usually plastic) to give it durability and improve appearance.
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L
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Lasering: The use of laser and chemicals to reach and alter inclusions in diamonds.
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O
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Oiling/Resin Infusion: The filling of surface breaking fissures with
colorless oil, wax, resin or other colorless substances, except glass
or plastic, to improve the gemstone's appearance.
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R
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Irradiation: The use of neutrons requiring an environmental safety release from
the Nuclear Regulatory Commission (NRC), Gamma and/or electron bombardment to
alter a gemstone's color. The irradiation may be followed by a heating process.
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U
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Diffusion: The use of chemicals in conjunction with high temperatures to produce
color and/or asterism producing inclusions.
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W
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Waxing/Oiling: The impregnation of a colorless wax, paraffin and oil in porous
opaque or translucent gemstones to improve appearance.
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SYNTHETIC STONES
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SYN
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The tag code may be used to describe "synthetic" materials that have essentially
the same optical, physical and chemical properties as a naturally occurring
counterpart. The code name may not be used as a noun; thus a stone must not be
referred to as a "synthetic." In all cases, the name of the stone must also be
used; thus, a stone must be referred to as "synthetic emerald," synthetic ruby,"
etc.
Synthetic stones are as stable in color and composition as their natural
counterpart.
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IMITATION PRODUCTS-SIMULANTS (SUBSTITUTES)
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IMIT
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"IMIT" is the tag code used for a manufactured product fabricated in such
materials as glass, ceramic or plastic designated to imitate or resemble the
appearance, but not duplicate the characteristic properties of a natural gemstone.
These materials require special care; avoid household chemicals, cosmetics,
abrasives and sudden shocks.
"IMIT" is also the tag code for a simulant, which is defined as a man-made single
crystal product that is used to simulate the appearance, but not duplicate the
properties of the natural gemstone it imitates.
Examples are: synthetic Spinel; synthetic Sapphire, synthetic Quartz and synthetic
Cubic Zirconia produced in various colors to imitate gemstones of different
species. This designation also includes GGG, strontium titanate and YAG.
This category also includes non-single crystal materials such as imitation Lapis
Lazuli and imitation Coral.
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ASSEMBLED MATERIALS (COMPOSITE)
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ASBL
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"ASBL" is the tag code for products made of multiple layers or combinations of
manufactured and/or natural materials fused, bonded or otherwise joined together
to increase stability and/or to imitate the appearance of a natural gemstone,
create a unique design or generate color combinations.
Examples:
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ASBL
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Opals-(various Combinations) Doublets and Triplets
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ASBL
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Garnet-Glass Doublets
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ASBL
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Sapphire-Synthetic Sapphire Doublets
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ASBL
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Colorless Beryl-joined by green bonding (Triplets)
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ASBL
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Mabe "Pearls" color coated, dyed, bleached, filled with hardened substances and a
Mother of Pearl back. Sometimes coating can be plastic or polymer to protect the
thin nacre.
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ASBL
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Bonded material such as Turquoise, Lapis, etc.
The "ASBL" coded stones require extra special care; avoid household chemicals,
cosmetics, abrasives and sudden shocks.
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GEMSTONE
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TAG CODE
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ENHANCEMENT METHOD
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FREQUENCY USED
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STABILITY
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CARE REQUIRED
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SPECIAL ADVICE
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Alexandrite
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N
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None
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-----
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----
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Normal
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Amazonite
|
E or W
I
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Impregnated with a colorless wax, paraffin or oil to improve appearance
Impregnated with plastic and other hardness resins to improve appearance
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Usually
Usually
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Good to fair
Very good
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Special
Special
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Avoid heat, chemical and ultrasonic
Avoid chemicals and ultrasonic
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Amber
|
E or H
D
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Heated to improve appearance, add "sun spangles" or deepen color
Dyed of surface treated to add color
|
Usually
Rarely
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Very good to Good
Variable
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Special
Special
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Avoid chemicals and ultrasonic
Avoid repolishing surface, chemicals and ultrasonic
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Amethyst
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E or H
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Heated to lighten color and/or to remove "Smokey" components
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Occasionally
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Excellent
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Special
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Some unheated material may fade in long exposure to sunlight
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Ametrine
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N
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None
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----
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----
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Normal
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Ammolite
|
I
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Impregnated with colorless hardened substances to increase stability
|
Usually
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Good to fair
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Special
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Avoid heat, household chemicals and ultrasonic
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Andalusite
|
N
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None
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----
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----
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Normal
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Aquamarine
|
E or H
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Heated to remove yellow components thereby producing a purer blue color
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Usually
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Excellent
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Normal
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Beryl
Blue
Pink
Yellow-Green
Red
Yellow
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R
E or H
N
E or O
R
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Irradiated blue from pale pink or colorless
Heated to remove yellow component thereby producing a pure pink color
None
The penetration of colorless oil and resins into fissures to improve appearance
Produced by irradiation
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Always
Commonly
-----------
Commonly
Usually
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Poor
Excellent
----------
Very good to fair
Variable
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Extra Special
Normal
Normal
Special
Normal/Special depending on method
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Color fades, avoid light and heat
Avoid high temperatures steam cleaning, chemicals and ultrasonic
Certain stones may fade in light or heat depending on method
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Chalcedony
Agate
Black
(Onyx)
Banded Blue
Green
Carnelian
Jasper
Chrysoprase |
D
D
D D
D
E
or H D
D
N |
Dyed
Dyed
Dyed Dyed
Dyed
Heated
to produce color Dyed to produce
color
Sometimes dyed to imitate other
stones None |
Usually
Always
Usually Commonly
Usually
Usually Occasionally
Occasionally
---- |
Excellent to Good Excellent to
Good Excellent Good to fair
Good to
fair
Excellent Excellent to
Good Excellent
----- |
Normal
Normal
Normal Special
Special
Normal Special
Normal
Normal |
Certain stones
may fade in light or heat Certain stones may
fade in light or heat
Certain stones may
fade in light or heat
Top |
Chrysoberyl Cat's
Eye
Transparent
Varieties: Yellow Brown Green |
R
N N N |
Irradiated to change
color
None None None |
Occasionally
----- ----- ----- |
Excellent
----- ----- ----- |
Normal
Normal Normal Normal |
For safety requirements,
if neutron irradiated, refer to code letter "R"
in gemstone information |
| Citrine |
E
or H |
Produced by heating various types of
quartz |
Usually |
Excellent |
Normal |
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Coral Black
White
Pink
Orange
"Gold"
Red |
N
E or B
E or
W
I
B
D |
None
Bleached
Impregnated
with colorless wax
Stabilized with
plastic to improve color and
durability Bleached from black
coral
Dyed |
-----
Commonly
Commonly
Commonly
Usually
Occasionally |
-----
Good
Good
Good
Very
Good
Variable |
Special
Special
Special
Special
Special
Special
to extra special depending on type of
dye |
Avoid chemicals,
cosmetics and ultrasonic Avoid chemicals,
cosmetics and ultrasonic: material may discolor
in time Avoid chemicals and
ultrasonic Same as above
Avoid
chemicals and ultrasonic Certain materials
may fade in light or heat. Avoid chemicals,
cosmetics and ultrasonic Top |
Diamond Colorless to
faint
Yellow
Colored |
L
C
F
HP
L
F
R
C
H |
Laser drilled to
improve appearance Coated to disguise
off-color
Filling of surface
cavities or fractures with a hardened
substance Use of heat with pressure to alter
color and/or clarity Laser drilled to improve
appearance Filling of surface cavities or
fractures with a hardened
substance Irradiated and/or heated to induce
"fancy" colors
Coated
to "fancy" colors
Use of heat to
alter color |
Occasionally to
common Rarely
Occasionally
Rarely
Occasionally
Rarely
Occasionally
Rarely
Rarely |
Very Good
Very
good to poor depending on method
Very
Good
Unknown
Very
good
Very good
Excellent to
very good
Fair to
poor
Unknown |
Normal
Variable
Special
Normal
Normal
Special
Normal
except
green
Special
Normal |
Recutting, steam
cleaning, ultrasonic and occasionally alcohol
may adversely affect color and
appearance Recutting or extreme heat may
remove filling
material
Recutting or extreme
heat may remove filling material Avoid
heating treated green stones as the color may
change. Some green stones have been radium
irradiate, for safety requirements refer to the
NRC. Recutting, steaming and ultrasonic may
adversely affect color and appearance Top |
| Diopside
(Chrome) |
N |
None |
---- |
---- |
Special |
Avoid
sudden temperature changes and harsh
chemicals |
| Emerald |
E or
O
D |
The penetration of
colorless oil, wax and resins into fissures to
improve appearance
Dyed with colored
agents |
Usually
Occasionally |
Very good to
fair
Variable |
Special
Special |
Avoid
sudden temperature changes, steaming, chemicals
and ultrasonic Same as above |
Garnet Almandite
Demantoid Grossularite Pyrope Rhodolite Spessarite Tsavorite |
N
N N N N N N |
None
None None None None None None |
----
---- ---- ---- ---- ---- ---- |
----
---- ---- ---- ---- ---- ---- |
Normal
Normal Normal Normal Normal Normal Normal |
Avoid
sudden temperature change Same as
above Same as above Same as above Same
as above Same as above Same as
above |
| Hematite |
N |
None |
---- |
---- |
Normal |
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| Iolite |
N |
None |
---- |
---- |
Normal |
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Ivory &
Bone
Mammoth
(Ivory) |
E or
B
D W
I |
Bleached to whiten and
remove discoloration
Dyed for artistic
purposes Impregnated with colorless paraffin
wax Impregnated with colorless hardened
substances to increase stability |
Commonly
Occasionally Occasionally
Commonly |
Good
Good Good
Good |
Special
Special Special
Normal |
Avoid
chemicals and ultrasonic: may discolor in
time Same as above Same as above Top |
Jade Jadeite
Green,
White and
Purple
Nephrite |
E or W
B and
W B and S D
D |
Coated with colorless
wax
Two-step bleaching and wax
impregnation Two-step bleaching and polymer
impregnation Dyed to imitate natural
colors
Dyed selectively to alter
color for artistic purposes in carvings |
Commonly
Rarely
Commonly
Occasionally
Rarely |
Fair
Poor
Very good
to good Variable
Unknown |
Normal to
Special Special
Special
Special
Special |
Avoid
ultrasonic
Avoid heat, chemicals and
ultrasonic same as above
Avoid strong
light, chemicals and ultrasonic: may discolor in
time. Avoid chemicals, ultrasonic and strong
light |
| Kunzite |
E or
H
R
|
Heated to improve color
from certain locations
Irradiated and
heated to darken color |
Commonly
Commonly |
Fair
Fair |
Special
Special |
Natural
and/or treated materials may fade-avoid strong
light, ultrasonic Same as above |
| Lapis
Lazuli |
E or W
D |
Coated with colorless wax
or oil to improve appearance Dyed to provide
color and/or uniformity |
Commonly
Commonly |
Fair
Variable |
Normal to
special Special |
Avoid
chemicals and ultrasonic Same as above Top |
| Malachite |
W
I |
Coated with colorless
wax
Impregnated with plastic and/or other
hardened agents to improve durability and
appearance |
Occasionally
Rarely |
Fair
Good |
Special
Special |
Avoid
chemicals and ultrasonic Same as
above
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| Moonstone |
N |
None |
---- |
---- |
Normal |
|
Opal White,
Black &
Semi-Black
Matrix
Boulder
Fire
Opal Cat's
Eye
Hydrophane
|
O
I
D
O
N I
O
D
I |
Impregnated with
colorless oil, wax and resins Impregnated
with colorless plastic to increase durability
& improve appearance Sugar solution
infilling in acid bath to darken background and
enhance color play and intensity Infusion of
unhardened essentially colorless substances into
voids to improve
appearance None Impregnated with colorless
resins to give durability and improve
appearance Impregnated with colorless oil,
wax and resins to hide crazing Impregnated
with hardened agents to improve appearance and
increase durability Impregnated with
colorless plastic to improve appearance and
increase durability |
Rarely
Rarely
Commonly
Occasionally
---- Usually
Commonly
Commonly
Commonly |
Fair
Good
Good
Fair
---- Good
Fair
Good
Good |
Special
Special
Special
Special
Special Special
Special
Special
Special |
Avoid
ultrasonic, heat and solvents Avoid heat and
solvents
Avoid solvents and
repolishing
Avoid heat, chemicals,
ultrasonic and repolishing Avoid
heat Avoid heat, solvents and
ultrasonic
Avoid heat, solvents and
ultrasonic Avoid heat and solvents Top
Avoid
heat and solvents |
Pearl Natural
Cultured
Mabe
'Pearl' |
E or
B
D
E or
B
D
D
D R
D
|
Bleached to improve
color and appearance Dyed with or without
chemical treatment combined with heat to produce
gray to black. Bleached to improve color and
uniformity of white color only Dyed to give
rose, blue or golden overtones Dyed blue,
black and other colors includes use of colored
nuclei Dyed all colors
(freshwater) Irradiated to produce blue, gray
black and bronze colors Chemical treatment
combined with heat to produce gray to
black See assembled materials |
Usually
Rarely
Usually
Usually
Occasionally
Usually Occasionally
Commonly |
Very good
Very
good to
good
Excellent
Good
Variable
Very
good Very good
Very good to good |
Special
Special
Special
Special
Special
Special Special
Special
Extra
Special |
Avoid
cosmetics and household chemicals Avoid
chemicals, cosmetics and ultrasonic
Same
as above
Same as above
Same as
above
Same as above Same as
above
Same as above
Avoid
household chemicals, cosmetics, abrasives and
sudden shocks |
| Peridot |
E or
O
F |
Penetration of colorless
oil, wax and resins into voids to improve
appearance
Filling of surface fractures
with a colorless hardened substance |
Rarely
Rarely |
Good to
fair
Good |
Special
Special |
Avoid
sudden temperature changes, harsh chemicals and
ultrasonic Same as above Top |
| Rhodonite |
D |
Dyed to "even out
color" |
Occasionally |
Poor |
Special |
Avoid
chemicals and ultrasonic |
| Ruby |
E or
H
D
F
R
U |
Heated to improve color
and appearance (Residue of foreign substance is
not visible under 10X
magnification.) Dyed with colored oil to
improve appearance Intentional filling of
surface cavities and fractures with a foreign
material, including glass which is visible under
10X magnification
Irradiated to change
color
Diffusion of color or asterism
in corundum at or near the surface |
Usually
Rarely
Commonly
Rarely
Rarely |
Excellent
Poor
Very
good to
fair
Unknown
Good |
Normal
Special
Special
Normal
Special |
Avoid household
chemicals and ultrasonic Fracture filling in
Rubies may be fragile and may fall out under
extreme pressure; avoid heat and
ultrasonic For safety requirements, if
neutron irradiated, refer to code letter
"R" Avoid repolishing or recutting |
| Sapphire |
E or
H
U
R |
Heated to produce,
intensity or lighten color and/or improve color
uniformity and appearance Diffusion of color
or asterism at or near the surface, usually
blue Irradiation to provide temporary intense
yellow or orange color |
Usually
Occasionally
Occasionally |
Excellent
Good
Very
Poor |
Normal
Special
Extra
Special |
Avoid repolishing or
recutting Fades quickly in light or
heat |
| Serpentine |
D E or W |
Dyed various
colors Impregnated with colorless wax |
Commonly Commonly |
Good to fair Very good
to good |
Special Special |
Dye may
fade Avoid ultrasonic Top |
| Sodalite |
D |
Dyed |
Rarely |
Fair |
Special |
Dye may
fade |
| Spinel |
N |
None |
---- |
---- |
Normal |
|
Spodumene Green
Yellow |
R
R |
Irradiated to produce
green color
Irradiated to produce yellow
color |
Rarely
Rarely |
Poor
Poor |
Extra
special
Extra special |
Color
fades in light or heat Same as
above |
| Sugilite |
N |
None |
---- |
---- |
Normal |
|
| Tanzanite |
E or H |
Heated to produce
violet-blue color |
Usually |
Excellent |
Special |
Avoid
sudden temperature changes |
Topaz Blue
Yellow/Orange
Pink/Red
Brown
Green
Green |
R
R
E
or H
N
R
U |
Irradiated brown and
often heated to produce blue
color
Irradiated to intensify
color
Heated chromium-bearing
pinkish-brown to orange
stones Normal
Irradiated to produce a
green color
Diffusion of color at or near
the surface |
Usually
Occasionally
Usually
----
Occasionally
Usually |
Excellent
Variable
Excellent
----
Poor
Good |
Normal
Special
Normal
Special
Extra
special
Special |
For
safety requirements, if neutron irradiated,
refer to code letter "R" Avoid heat and
strong light
May fade in exposure to
sunlight Color fades in exposure to
sunlight Avoid repolishing or
recutting |
Tourmaline Chrome
Vanadium Cat's
Eye Yellow/Orange
Green,
Blue
Pink, Red, Purple |
N N E or
H R E or H O
E or
H R O
D |
None None Heated
to improve color Irradiated to improve
color Heated to improve color The
penetration of colorless oil or resins into
voids to improve appearance Heated to improve
color Irradiated to intensify
color Penetration of colorless oil or
unhardened resins into voids to improve
appearance Penetration of coloring agents
into voids to improve appearance |
---- ---- Rarely Rarely Commonly
Occasionally
Occasionally Commonly Occasionally
Occasionally |
---- ---- Excellent Very
Good Excellent Good to
fair
Excellent Good Good to
fair
Fair to poor |
Normal Normal Normal Normal Normal Special
Normal Normal Special
Special |
Top
Avoid
temperature changes, steaming, chemicals and
ultrasonic
Same as
above
Same as above |
| Turquoise |
I
W
D |
Impregnated with plastic
to create or improve color and increase
durability Impregnated with colorless oil or
wax to enhance or create color Dyed to
improve color |
Commonly
Commonly
Rarely |
Good
Fair to
poor
Poor |
Special
Special
Extra
special |
Avoid hot
water and household chemicals
Same as
above
Same as above |
Zircon Green,
Brown Yellow Blue and
colorless
Red |
N E or
H E or H
E or H |
None Heated to improve
color Brownish crystals are heated to these
colors Heated to change brownish crystal to
red |
---- Rarely Always
Commonly |
---- Good Fair to
poor
Fair to poor |
Special Special Special
Special |
Avoid harsh
abrasives Same as above Same as
above
Same as
above |