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Colored Stones Exam > GIA Colored Stones Exam 51-100 > Flashcards

GIA Colored Stones Exam 51-100 Flashcards

1
Q

The lapis lazuli trade grade that’s often spotted with green and shows obvious calcite is called ________ .

A

Chilean

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2
Q

The finest color of turquoise is ______________ .

A

Intense medium blue

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3
Q

The purest blue colors of turquoise are caused by _________ .

A

copper

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4
Q

What is the trade term for top_color turquoise?

A

Persian

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5
Q

Turquoise usually forms in __________ .

A

Limonite

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6
Q

What is the color of the markings that sandstone matrix creates in turquoise?

A

tan

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7
Q

Stabalized turquoise is a tade term for what?

A

Polymer_impregnated turquoise

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8
Q

A new turquoise treatment that appeared in the 1980’s and has been used to treat more thabn 10 million carats is _____________ .

A

Zachary method

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9
Q

The major source of turquoise today is ___________ .

A

Southwestern US.

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10
Q

Reconstructed turquoise is __________ .

A

Immitation

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11
Q

Malachite’s color is caused by what element?

A

Copper

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12
Q

The only commercial source of charolite is in what country/

A

Russia

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13
Q

Chalcedony with curved or irregular bands or layers that differ in color and transparency.

A

Agate

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14
Q

A crystal growth habit with a bumpy appearance similar to a bunch of grapes.

A

Botryodal

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15
Q

A cryptocrystalline quartz aggregate.

A

Chalcedony

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16
Q

A property of some crystals that causes them to vibrate at a constant frequency when subjected to an electrical current.

A

Piezoelectricity

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17
Q

A type of sagenitic quartz containing needle_like rutile inclusions.

A

Rutilated quartz

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18
Q

A transparent quartz; usually rock crystal; that contains eye_visable inclusions; often named according to the type of inclusions it contains.

A

Sagenitic

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19
Q

A table_cut gem with a flat or slightly domed top and sometimes a carved design; typically set in men’s rings and cufflinks.

A

Signet

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20
Q

A type of sagenitic quartz containing needle_like or rod_like tourmaline inclusions.

A

Tourmalated quartz

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21
Q

Cryptocrystalline quartz is known as ___________ .

A

Chalcedony

22
Q

Chalcedony with curved or irregular bands or layers that differ in color and transparency is known as ________ .

A

Agate

23
Q

What type of crystalline has the smallest crystal size?

A

Cryptocrystalline

24
Q

In the nineteenth century; a major source of amethyst was discovered in what country?

A

Brazil

25
Q

The color of amethyst results from __________________ .

A

Color centers acting on iron .

26
Q

One of amethyst’s finest colors is _____________________ .

A

medium_dark strong reddish purple.

27
Q

What country is the major source for commercial_quality amethyst?

A

Brazil

28
Q

Maraba amethyst is often

A

Uniform in color

29
Q

What treatment lightens dark amethyst?

A

heat

30
Q

How is most of the citrine on the market produced?

A

By heating amethyst

31
Q

What country is the source for natural ametrine?

A

Bolivia

32
Q

What type of aggregate is tiger’s eye quartz?

A

microcrystalline

33
Q

Multiple slender crystals or channels cause this in cat’s_eye chacelony.

A

Chatoyancy

34
Q

What is the color of chrysoprase?

A

Yellowish green

35
Q

Treated black chalcedony is also known by the trade term ____________ .

A

Black onyx

36
Q

The trade considers what gemstone to have the finest green among the colored stones?

A

Emerald

37
Q

When all factors are equal; a great difference in emerald value can be caused by slight differences in __________; ____________ and ____________ .

A

hue; tone and saturation.

38
Q

Emerald’s color_causing trace elements are _________ ; __________ and ___________ .

A

Chromium; Vanadium; Iron

39
Q

What can cause a great reduction in a finished emerald’s value?

A

Poor cutting

40
Q

The trade accepts the fact that most emeralds contain _____________ .

A

Eye visable inclusions

41
Q

Inclusions that make an emerald less valuable also make it less _____________ .

A

Transparent.

42
Q

How are emerald’s fractures usually filled?

A

Oil; Resin; Both

43
Q

What type of emerald commands premium prices?

A

Untreated

44
Q

What is the safest way to clean emeralds?

A

Gentle scrubbing with warm soapy water.

45
Q

What two countries account for 75% of emerald purchases worldwide?

A

The US and Japan.

46
Q

What four countries provide most of the world’s emeralds?

A

Brazil; Columbia; Zambia; Zimbabwe

47
Q

The world’s emeralds are judged by what country’s finest?

A

Columbia

48
Q

What country’s emerald mines have fewer fractures than emeralds from other sources?

A

Africa

49
Q

What is the most common emerald imitation used in jewelry?

A

Synthetic spinel triplets

50
Q

What two methods are used to synthesize emeralds?

A

Flux and hydrothermal

Colored Stones Exam (15 decks)

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