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GIA-Colored Stones > GI 12: Detecting Gem Treatments > Flashcards

GI 12: Detecting Gem Treatments Flashcards

1
Q

Gem treatments are done for what reason?

A

Usually done to improve a stone’s appearance

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2
Q

What would most likely be found in heat-treated corundum (2)?

A
  1. Discoid Fractures
  2. Broken Silk
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3
Q

An intense concentration of color around an included crystal that results when the crystal releases titanium during treatment is called what?

A

Bleeding

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4
Q

What might help you find oil or resin fillers in emerald?

A

Fluorescence

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5
Q

What are 2 gems that are routinely irradiated to improve color?

A
  1. Red Tourmaline
  2. Blue Topaz
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6
Q

Which gem treatment is probably the most widely used today?

A

Heat Treatment

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7
Q

When irradiation is used to enhance a gem’s color it is…

A

Usually undetectable

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8
Q

Typical signs of treatment with lattice diffusion include what?

A

Color concentrations along facet junctions

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9
Q

Separating naturally colored green from treated-colored green diamonds is…

A

is often impossible.

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10
Q

Colorless impregnation is used to do what (2)?

A
  1. Improve appearance
  2. Improve stability
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11
Q

After a diamond is irradiated, its color might be further altered by..

A

Annealing

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12
Q

Most origin-of-color tests on diamonds should be done by…

A

by a gemological laboratory

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13
Q

Natural jadite that’s untreated is known as what?

A

Type A

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14
Q

Black onyx is actually

A

dyed black chalcedony

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15
Q

Sugar and smoke opal treatments do what?

A

Darken the stone and bring out its play-of-color

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16
Q

Definition:

A treatment that uses chemicals to lighten or remove color

A

Answer:

Bleaching

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17
Q

Definition:
Intense color concentration around a crystal that results when the crystal releases titanium during heat treatment

A

Answer:

Bleeding

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18
Q

Definition:
Diffuse and patchy remains of rutile needles that were partially melted by heat treatment of corundum.

A

Answer:

Broken Silk

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19
Q

Definition:

Filling of pores or other openings with melted wax, resin, polymer, or plastic to improve appearance and stability

A

Answer:

Colorless Impregnation

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20
Q

Definition:

A circular stress fracture that occurs when heat causes and inclusion to expand more than its host gem

A

Answer:

Discoid Fracture

21
Q

Definition:

A treatment that adds color or affects color by deepening it, making it more even, or changing it

A

Answer:

Dyeing

22
Q

Definition:

Using a filler to concel fractures and improve the apparent clarity of a gem

A

Answer:

Fracture (fissure) filling

23
Q

Definition:

A chemical that treaters mix with some resins to cause them to solidify

A

Answer:

Hardener

24
Q

Definition:

Exposing a gem to rising temperatures for the purpose of changing its appearance

A

Answer:

Heat treatment

25
Q

Definition:

Diamond color modification that uses equipment and conditions similar to those used to grow synthetic diamonds

A

Answer:

High Pressure, High Temperature (HPHT)

26
Q

Definition:

Exposing a gem to radiation to change or improve its color

A

Answer:

Irradiation

27
Q

Definition:

Using a concentrated beam of laser light to reach a diamond’s dark inclusions and disguise or eliminate them

A

Answer:

Laser Drilling

28
Q

Definition:

A treatment in which a gem is exposed to high temperatures and chemicals to let color-causing elements penetrate its surface

A

Answer:

Lattice Diffusion

29
Q

Definition:

The remains of a mineral inclusion that was altered by heat treatment

A

Answer:

Melt relic

30
Q

Definition:

Tinting a cultured pearl with a red dye

A

Answer:

Pinking

31
Q

Definition:

Heating a wrapped opal until smoke or ash penetrates its surface to darken it and bring out its play-of-color

A

Answer:

Smoke Treatment

32
Q

Definition:

Soaking an opal in a hot sugar solution and then in sulfuric acid to darken it and bring out its play-of-color

A

Answer:

Sugar Treatment

33
Q

Definition:

Altering a gem’s appearance by applying a backing, coating, or coloring agent like paint

A

Answer:

Surface modification

34
Q

Definition:

Any human-controlled process, beyond cutting and polishing, that improves the appearance, durability, or value of a gem

A

Answer:

Treatment

35
Q

Definition:

Natural jadeite that’s untreated or enhanceds only wth a surface coating of wax

A

Answer:

Type A Jadite

36
Q

Definition:

Natural jadeite that’s bleached in acid to remove undesireable staining, then impregnated with wax or polymers

A

Answer:

Type B Jadeite

37
Q

Definition:

Natural jadeite that’s dyed and often bleached and impregnated with wax or polymers

A

Answer:

Type C Jadeite

38
Q

What is one of the oldest gem treatments and probably the most widely used today?

A

Heat Treatment

39
Q

How can you tell if corundum was heat-treated?

A

By examining its inclusions under magnification

40
Q

What does HPHT treatment do? (list 2)

A
  1. Eliminate the color of brownish diamonds
  2. Create fancy diamond colors
41
Q

T/F: The gem industry requires disclosure of fracture filling?

A

True

42
Q

Of all the colored stones, what gem is probably the one that’s most commonly treated by fracture filling?

A

Emerald

43
Q

What are some signs of oil or resin fillers? List 4

A
  1. Flash effect
  2. Fluorescence
  3. Trapped bubbles
  4. Seepage of the filler
44
Q

What is the most common diamond treatment?

A

Fracture filling

45
Q

What are 3 signs of fracture filling in a diamond?

A
  1. flash effect
  2. trapped bubbles
  3. crackled texture
46
Q

What are 2 signs of glass-filled cavities in corundum?

A
  1. Glassy residue
  2. Readily visible bubbles
47
Q

Most orign-of-color tests should be done by…

A

a gemological laboratory

48
Q

What are 2 effects of modern diamond irradiation?

A
  1. leave little or no color zoning
  2. no measurable radioactivity

GIA-Colored Stones (10 decks)

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