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Enhancement of Gemstones


Gemstone enhancement is defined as any treatment process that is used to improve the appearance, durability or availability of a gemstone.
Many gemstones available on the market today are routinely enhanced to impart color, clarity or strength to the stone.

The term "gemstone enhancement" should not be confused with terms such as synthetic, lab-grown, man-made or any other
term which infers the creation of materials.

Natural gemstones are created by natural processes within the earth.
Man-made, lab-grown (or laboratory), or synthetic gems are those created by any non-natural process.

Enhancements of a gemstone can be used on natural or synthetic materials to improve their appearance.
However, a natural gemstone that is enhanced is still considered a Natural gemstone, whereas a synthetic/man-made stone
can never be considered natural whether or not is has received an additional treatment.

The chart below shows the various labels applied to gemstones which denote various enhancement processes.

ENHANCEMENT is defined as any traditional process other than cutting and polishing that improves the
appearance (such as 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.

Those which are not enhanced
N 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.
Those which are not normally enhanced.
E 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.

SYMBOLS FOR SPECIFIC FORMS OF ENHANCEMENTS:
B Bleaching: The use of heat, light and/or other agents to lighten or remove a gemstone's color.
C 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.
D Dyeing: The introduction of coloring matter into a gemstone to give it new color, intensify present color or improve color uniformity.
F 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.
H 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.)
HP Heating and Pressure: The use of heat and pressure combines to affect desired alterations of color and/or clarity.
I Impregnation: The impregnation of a porous gemstone with a colorless agent (usually plastic) to give it durability and improve appearance.
L Lasering: The use of laser and chemicals to reach and alter inclusions in diamonds.
O 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.
R 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.
U Diffusion: The use of chemicals in conjunction with high temperatures to produce color and/or asterism producing inclusions.
W Waxing/Oiling: The impregnation of a colorless wax, paraffin and oil in porous opaque or translucent gemstones to improve appearance.
SYNTHETIC STONES
SYN 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.

IMITATION PRODUCTS-SIMULANTS (SUBSTITUTES)
IMIT "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.

Example 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.

ASSEMBLED MATERIALS (COMPOSITE)
ASBL "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:

ASBL Opals-(various Combinations) Doublets and Triplets
ASBL Garnet-Glass Doublets
ASBL Sapphire-Synthetic Sapphire Doublets
ASBL Colorless Beryl-joined by green bonding (Triplets)
ASBL 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.
ASBL Bonded material such as Turquoise, Lapis, etc.

The "ASBL" coded stones require extra special care; avoid household chemicals, cosmetics, abrasives and sudden shocks.


Various Gemstones and their possible enhancements

GEMSTONE TAG
CODE
ENHANCEMENT
METHOD
FREQUENCY USED STABILITY CARE REQUIRED SPECIAL
ADVICE
Alexandrite N None ----- ---- Normal
Amazonite E or W


I
 
Impregnated with a colorless wax, paraffin or oil to improve appearance
Impregnated with plastic and other hardness resins to improve appearance
Usually


Usually
Good to fair


Very good
Special


Special
Avoid heat, chemical and ultrasonic

Avoid chemicals and ultrasonic
Amber E or H

D
 
Heated to improve appearance, add "sun spangles" or deepen color
Dyed of surface treated to add color
Usually

Rarely
Very good to Good
Variable
Special

Special
Avoid chemicals and ultrasonic
Avoid repolishing surface, chemicals and ultrasonic
Amethyst E or H
 
Heated to lighten color and/or to remove "Smokey" components Occasionally Excellent Special Some unheated material may fade in long exposure to sunlight
Ametrine N None ---- ---- Normal
Ammolite I Impregnated with colorless hardened substances to increase stability Usually Good to fair Special Avoid heat, household chemicals and ultrasonic
Andalusite N None ---- ---- Normal
Aquamarine E or H Heated to remove yellow components
thereby producing a purer blue color
Usually Excellent Normal
Beryl
Blue

 
Pink



Yellow-Green
Red


Yellow

R


E or H



N
E or O


R

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

Always


Commonly



-----------
Commonly


Usually

Poor


Excellent



----------
Very good to fair

Variable

Extra Special


Normal



Normal
Special


Normal / Special depending on method

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
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

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
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
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 irradiated.
For safety requirements refer to the NRC.
Recutting, steaming and ultrasonic may adversely affect color and appearance
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
Iolite N None ---- ---- Normal
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
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
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
 
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

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
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
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




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


GEMSTONE PROPERTIES AND ENHANCEMENTS

MATERIAL SPECIFIC GRAVITY HARDNESS REFRACTIVE INDEX ENHANCEMENT SPECIAL CARE
Normal Range Bire. Most Commonly Used Method Code
Alexandrite 3.73 ±.02 8 ½ 1.746 – 1.755 +.004
–.006
.008–
.010
None A Normal
Amethyst 2.66 +.03
–.02
7 1.544 – 1.553 ±.000 .009 None A Normal
Andalusite 3.17 ± .04 7 - 7 ½ 1.634 - 1.643 ±.005 .007–
.013
None A Normal
Aquamarine 2.72 +.18
–.05
7 ½ - 8 1.577 - 1.583 ±.017 .005–
.009
Heated H Normal
Ametrine 2.66 +.03
–.02
7 1.544 - 1.553 ±.000 .009 None A Normal
Beryl 2.72 +.18
–.05
7 ½ - 8 1.577 - 1.583 ±.017 .005–
.009
None A Normal
Chrysoberyl 3.73 ±.02 8 ½ 1.746 - 1.755 +.004
–.006
.008–
.010
None A Normal
Citrine 2.66 +.03
–.02
7 1.544 - 1.553 ±.000 .009 Heated H Normal
Diamond 3.52 ±.01 10 2.417 --- --- None A Normal
Emerald 2.72 +.18
–.05
7 ½ - 8 1.577 - 1.583 ±.017 .005–
.009
Oiled O Avoid temp. changes, steaming, chemicals and ultrasonic.
Garnet 3.78 +.09
–.16
7 - 7 ½ 1.746 +.010
–.026
--- None A Avoid sudden temperature changes.
Iolite 2.61 ±.05 7 - 7 ½ 1.542 - 1.551 +.045
–.011
.008–
.012
None A Normal
Kunzite 3.18 ±.03 6 ½ - 7 1.660 - 1.676 ±.005 .014–
.016
Irradiated R Avoid strong light and ultrasonic - color may fade
Opal 2.15 +.08
–.90
5 - 6 ½ 1.450 +.020
–.080
--- None A Avoid heat, chemicals and ultrasonic.
Peridot 3.34 +.14
–.07
6 ½ - 7 1.654 - 1.690 ±.020 .035–
.038
None A Avoid sudden temperature changes and chemicals.
Rhodolite 3.84 ±.10 7 - 7 ½ 1.760 +.010
–.020
--- None A Avoid sudden temperature changes.
Rubellite 3.06 +.20
–.06
7 - 7 ½ 1.624 - 1.644 +.011
–.009
.018–
.040
Irradiated R Normal
Ruby 4.00 +.10
–.05
9 1.762 - 1.770 +.009
–.005
.008–
.010
Heated H Normal
Sapphire 4.00 +.10
–.05
9 1.762 - 1.770 +.009
–.005
.008–
.010
Heated H Normal
Spinel 3.60 +.10
–.03
8 1.718 ±.017 --- None A Normal
Tanzanite 3.35 +.10
–.25
6 - 7 1.691 - 1.700 ±.005 .008–
.013
Heated H Avoid sudden temperature changes and ultrasonic.
Tsavorite 3.61 +.12
–.04
7 - 7 ½ 1.740 +.020
–.010
--- None A Avoid sudden temperature changes.
Topaz 3.53 ±.04 8 1.619 - 1.627 ±.010 .008–
.010
Irradiated & Heated R Normal
Tourmaline 3.06 +.20
–.06
7 - 7 ½ 1.624 - 1.644 +.011
–.009
.018–
.040
Heated H Normal
Zircon 4.70 +.03
–.80
6 - 7 ½ 1.925 - 1.984 +.040
–.145
.000–
.059
Heated H Avoid Abrasives