Any human-controlled process other than cutting and polishing that improves the appearance (color/clarity/phenomena),
durability, or value of a gemstone. Many in the trade call them “Enhancements”, but the US Federal Trade Commission
(FTC)-as well as many gem professionals consider “treatment” the more accurate term.
Gems are treated for a number of different reasons:
A: Annealing:- A Controlled heating and cooling process called annealing. It is another way to change the diamond color. When it follows irradiation in a two-step process, annealing modifies irradiated colors to produce brown, orange, or yellow. Rarely, it can also produce shades of pink, red, or purple, and create black diamonds by inducing large-scale graphitization within surface-reaching fractures.
ASBL: (Assemble):- Material made up of more than one material. Some or all components can be natural but still
bonded together. Doublet or Triplet. Doublet: Two separate pieces of material fused or cemented together to form a
single assembled stone. Triplet: A single assembled stone made from three separate pieces of material fused or
B: Bleaching:- Uses chemicals to lighten or remove color.
C: Coating/surface modification - Surface modification as lacquering, backing, coloring or sputtering of
films to improve appearance, provide color or add other special effects.
CMP: Composite:- Material made from two or more constituent materials with significantly different physical
or chemical properties or layers assembled by bonding or other artificial methods.
D: Dyeing:- Adds color or affects color by deepening it, making it more even, or improving color uniformity.
F: Fracture (often called fissure) filling:- Using a filler (colorless oils, glass, plastic, resins, polymers,
hardener solidified borax or similar substances) to conceal fractures and improve the apparent clarity of a gem.
GF: Glass-filled:- Glass-filled or composite ruby or sapphire: fractures filled with high-lead-content glass,
which made them appear very transparent. Performed at lower temperatures, this is a less durable treatment
and should be treated gently, avoiding household and professional chemicals.
H: Heat Treatment:- Exposing a gem to rising temperatures for the purpose of changing its appearance.
This is an old process, and 95% of corundum, all tanzanite, zircon, aquamarine, and amber are often heated.
Heat treatments are generally stable.
HP: Heating & Pressure:- The use of temperature and pressure combined to effect desired alteration of color,
clarity or phenomena.
Hydro: Hydrothermal Growth:- A process in which nutrients(natural quartz seed crystals) dissolve in a water
solution and chemicals at high temperature and pressure, and cool to form synthetic crystals. the first hydrothermal
quartz appeared in laboratories in the 1890s. hydrothermal synthetic emeralds for jewelry came in the 1960s.
I: Impregnation:- Filling of a porous gemstone or other openings with melted wax, resins, polymer, or plastic to
improve appearance and stability. Some dealers called stabilization as well.
L: Lasering:- A clarity treatment that uses a concentrated beam of laser light to reach a gemstone’s dark
inclusions and disguise or eliminate them. Usually diamond.
O: Oiling / Resin:- The filling of surface-breaking fissures with colorless oil, wax & resin.
R: Irradiation - Exposing a gem to electromagnetic radiation X-rays or gamma rays or subatomic particles
(neutrons or electrons) to change a gemstone’s color. The color centers aren’t always permanent. In some cases,
heat or light can destroy them and remove the color. Irradiated blue topaz made a big impact on the market in the 1980s.
SIM: Simulated:- Any gemstone has a wide variety of less expensive look-alike same materials. Some of them come
from the ground and some from the lab. The imitations are called simulated and are used in their place.
SYN: Synthetic gem:- Made in laboratories, but they have essentially the same chemical composition, crystal
structure, and properties as their natural counterpart.
SC: Special care:- Avoid chemicals, heat, and light, and don’t use ultrasonic cleaner or steamer. Clean with warm
soapy water and a soft brush or cloth.
U: Lattice Diffusion/Diffusion:- Experimentation during the 1980s, Lattice diffusion treatment is applied to
colorless or very light-colored natural corundum, especially sapphire which doesn’t respond to normal heat treatment.
Treaters place faceted corundum in a crucible containing a coloring agent like titanium or chromium. Temperature
approaching 3700°F (2050°c) melting point of corundum with iron and titanium oxides to create blue stones and
chromium to create red stones.Beryllium diffusion is newer corundum treatment that results in a wide range of colors.
Including pinkish-orange (padparadscha), orange, yellow, red, and blue.
W: Waxing/oiling in opaque stones:- Wax and oil in porous opaque or translucent gemstones to improve appearance.
Sugar & smoke Treatment:- There are two different treatments that darken opals and bring out their play-of-color, called
sugar and smoke treatment.
Smoke:- Heating a wrapped opal until smoke or ash penetrates its surface to darken it and bring out its play-of-color.
Sugar:-Soaking an opal in a hot sugar solution and then sulfuric acid to darken it and bring out its play of color.
Gemstone Enhancement Codes* N= Not Enhanced, B= Bleaching, C = Coating, D = Dyeing, F = Filling, H =
Heating, HP = Heat & Pressure, I = Impregnation, L = Lasering, O =
Oiling/Resin, R = Irradiation,U = Diffusion, SC = Special Care, ASBL =
Assembled,CMP = Composite, W= Waxing/Oiling in Opaque Stones
*Codes and types of treatments must only be used as directed in the
Gemstone Information Manual, available at www.agta.org and www.gia.edu.