GI 12: Detecting Gem Treatments Flashcards
Gem treatments are done for what reason?
Usually done to improve a stone’s appearance
What would most likely be found in heat-treated corundum (2)?
- Discoid Fractures
- Broken Silk
An intense concentration of color around an included crystal that results when the crystal releases titanium during treatment is called what?
Bleeding
What might help you find oil or resin fillers in emerald?
Fluorescence
What are 2 gems that are routinely irradiated to improve color?
- Red Tourmaline
- Blue Topaz
Which gem treatment is probably the most widely used today?
Heat Treatment
When irradiation is used to enhance a gem’s color it is…
Usually undetectable
Typical signs of treatment with lattice diffusion include what?
Color concentrations along facet junctions
Separating naturally colored green from treated-colored green diamonds is…
is often impossible.
Colorless impregnation is used to do what (2)?
- Improve appearance
- Improve stability
After a diamond is irradiated, its color might be further altered by..
Annealing
Most origin-of-color tests on diamonds should be done by…
by a gemological laboratory
Natural jadite that’s untreated is known as what?
Type A
Black onyx is actually
dyed black chalcedony
Sugar and smoke opal treatments do what?
Darken the stone and bring out its play-of-color
Definition:
A treatment that uses chemicals to lighten or remove color
Answer:
Bleaching
Definition:
Intense color concentration around a crystal that results when the crystal releases titanium during heat treatment
Answer:
Bleeding
Definition:
Diffuse and patchy remains of rutile needles that were partially melted by heat treatment of corundum.
Answer:
Broken Silk
Definition:
Filling of pores or other openings with melted wax, resin, polymer, or plastic to improve appearance and stability
Answer:
Colorless Impregnation
Definition:
A circular stress fracture that occurs when heat causes and inclusion to expand more than its host gem
Answer:
Discoid Fracture
Definition:
A treatment that adds color or affects color by deepening it, making it more even, or changing it
Answer:
Dyeing
Definition:
Using a filler to concel fractures and improve the apparent clarity of a gem
Answer:
Fracture (fissure) filling
Definition:
A chemical that treaters mix with some resins to cause them to solidify
Answer:
Hardener
Definition:
Exposing a gem to rising temperatures for the purpose of changing its appearance
Answer:
Heat treatment
Definition:
Diamond color modification that uses equipment and conditions similar to those used to grow synthetic diamonds
Answer:
High Pressure, High Temperature (HPHT)
Definition:
Exposing a gem to radiation to change or improve its color
Answer:
Irradiation
Definition:
Using a concentrated beam of laser light to reach a diamond’s dark inclusions and disguise or eliminate them
Answer:
Laser Drilling
Definition:
A treatment in which a gem is exposed to high temperatures and chemicals to let color-causing elements penetrate its surface
Answer:
Lattice Diffusion
Definition:
The remains of a mineral inclusion that was altered by heat treatment
Answer:
Melt relic
Definition:
Tinting a cultured pearl with a red dye
Answer:
Pinking
Definition:
Heating a wrapped opal until smoke or ash penetrates its surface to darken it and bring out its play-of-color
Answer:
Smoke Treatment
Definition:
Soaking an opal in a hot sugar solution and then in sulfuric acid to darken it and bring out its play-of-color
Answer:
Sugar Treatment
Definition:
Altering a gem’s appearance by applying a backing, coating, or coloring agent like paint
Answer:
Surface modification
Definition:
Any human-controlled process, beyond cutting and polishing, that improves the appearance, durability, or value of a gem
Answer:
Treatment
Definition:
Natural jadeite that’s untreated or enhanceds only wth a surface coating of wax
Answer:
Type A Jadite
Definition:
Natural jadeite that’s bleached in acid to remove undesireable staining, then impregnated with wax or polymers
Answer:
Type B Jadeite
Definition:
Natural jadeite that’s dyed and often bleached and impregnated with wax or polymers
Answer:
Type C Jadeite
What is one of the oldest gem treatments and probably the most widely used today?
Heat Treatment
How can you tell if corundum was heat-treated?
By examining its inclusions under magnification
What does HPHT treatment do? (list 2)
- Eliminate the color of brownish diamonds
- Create fancy diamond colors
T/F: The gem industry requires disclosure of fracture filling?
True
Of all the colored stones, what gem is probably the one that’s most commonly treated by fracture filling?
Emerald
What are some signs of oil or resin fillers? List 4
- Flash effect
- Fluorescence
- Trapped bubbles
- Seepage of the filler
What is the most common diamond treatment?
Fracture filling
What are 3 signs of fracture filling in a diamond?
- flash effect
- trapped bubbles
- crackled texture
What are 2 signs of glass-filled cavities in corundum?
- Glassy residue
- Readily visible bubbles
Most orign-of-color tests should be done by…
a gemological laboratory
What are 2 effects of modern diamond irradiation?
- leave little or no color zoning
- no measurable radioactivity
