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Colored Stones Exam > GIA Colored Stones Exam 151-200 > Flashcards

GIA Colored Stones Exam 151-200 Flashcards

1
Q

What are the most widespread minerals on earth?

A

Feldspars

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2
Q

How many cleavage directions are found in feldspar; spodumene and diopside?

A

Two

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3
Q

What three basic chemical elements do all feldspars contain?

A

aluminum; oxygen; silicon

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4
Q

Moonstone is a variety of ________ .

A

Orthoclase

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5
Q

In which era did moonstone go out of style?

A

Art Deco

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6
Q

What color is the finest adularescence of the finest moonstone?

A

Blue

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7
Q

Tiny tension cracks in moonstone are called what?

A

Centipedes

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8
Q

Rainbow moonstone is a trade term for a type of ________ .

A

Labradorite

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9
Q

Spectrolite is a variety of _________ .

A

Labrodorite

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10
Q

The greenish blue feldspar that has gridlike white streaks and resembles turquoise is called __________ .

A

Amazonite

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11
Q

Medium green.

A

Hiddenite

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12
Q

The scattering of light by stacked; alternating mineral layers?

A

Moonstone’s adularescence

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13
Q

What selling point is used for sunstone from Oregon?

A

It isn’t treated

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14
Q

The high clarity and lack of treatment make what stone an attractive emerald alternative?

A

Chrome diopside.

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15
Q

What causes sunstone’s redish or golden sheen?

A

small inclusions

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16
Q

What causes sunstone’s glittering reflections?

A

larger inclusions

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17
Q

Intense pink and intense violetish purple.

A

Kunzite

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18
Q

Opal is composed of primarily of __________ .

A

Silica

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19
Q

When did most opal form?

A

15 to 30 million years ago.

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20
Q

What is the percentage of water that most opal contains?

A

3 to 10 percent

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21
Q

What is semi_black opal’s background color?

A

grayish

22
Q

What is the transparency of gray_based black opal?

A

opaque

23
Q

What is the transparency range of white opal?

A

translucent to opaque

24
Q

The type of matrix found as a layer in finished boulder opal is comprised of __________ .

A

ironstone

25
Q

Experts think fire opal’s background color is caused by _________ .

A

Iron impurities

26
Q

In opal; a pattern of large distinct; usually rectangular patches of play_of_color with edges that touch each other is called __________ .

A

Harlequin

27
Q

Play_of_color that’s seen only when light travels through an opal to the eye is called _________ .

A

Contra luz

28
Q

Where were the first black opals discovered?

A

New South Wales; Australia

29
Q

What is the first step in evaluating an opal?

A

Determine its type

30
Q

Which treatment involves immersing opal in concentrated sulfuric acid?

A

sugar

31
Q

Who created the first marketable synthetic opal>

A

Pierre Gilson

32
Q

Plastic imitation opal was first marketed in the late 1980’s in what country?

A

Japan

33
Q

What is precious opal made of?

A

Billions of uniform; submicroscopic silica spheres; stacked in an orderly pattern.

34
Q

What type of opal commands the highest prices?

A

black

35
Q

What type of opal makes up the bulk of commercial_quality on the market?

A

white

36
Q

What makes boulder opal the most durable?

A

the matrix backing

37
Q

Uniform red_orange to bright red color

A

Finest fire opal

38
Q

What is one of the few opal types that is cut into a faceted gem?

A

fire opal

39
Q

What three things combine to create and opal’s unique beauty?

A

Color; Pattern; Clarity

40
Q

How are opals divided into types?

A

by background color

41
Q

What is the rarest play_of_color?

A

Displays hues across the entire spectrum.

42
Q

What is considered the most valuable play_of_color hue?

A

red

43
Q

In general what is the most preferred play_of_color pattern?

A

large; closely arranged color patches.

44
Q

What percentage of the world’s total opal supply comes from Australia?

A

90%

45
Q

What country is the major source for fire opal?

A

Mexico

46
Q

Commercial_quality white opal dominates what country’s market?

A

the US

47
Q

What three things should be kept consistant when evaluating opal?

A

conditions; methods; samples

48
Q

In opal; very small patches or “dots” of play_of_color is known as _________ .

A

Pinfire

49
Q

Large areas of play_of_color is called _______ .

A

Flash

50
Q

An opal with a gray background that appears opaque is known as a __________ .

A

Semi_black opal

Colored Stones Exam (15 decks)

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