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Colored Gems > Terms > Flashcards

Terms Flashcards

1
Q

The term used to describe a gem that is colored by trace elements in its crystal structure is

A

allochromatic. In an allochromatic gem, the pure state can be colorless, and color is only achieved when certain trace elements are present in the crystal lattice

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2
Q

In gems, phenomena caused by structure are the result of

A

interference. Interference is the interaction between two light rays with the same wavelength as they travel along the same path.
ie Moonstone, labradorite, opal

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3
Q

The characteristic shape of a gem crystal is called its

A

habit. A mineral’s characteristic shape, or habit, depends on its growing conditions.

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4
Q

The type of deposit that’s most likely to be found miles away from the original source rock is

A

An alluvial deposit is a type of secondary deposit where gems have been eroded from the source rock and transported by water far from their source.

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5
Q

Which is a workable alluvial deposit of gem minerals with economic potential?

A

placer. When an alluvial deposit shows economic potential, miners refer to it as a placer.

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6
Q

The kinds and relative quantities of atoms that make up a material are defined as its

A

chemical composition. The kinds and relative quantities of atoms that make up a material are defined as its chemical composition

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7
Q

A rock must

A

Rocks are composed of masses of one or more kinds of mineral crystals

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8
Q

A regular, repeating internal arrangement of atoms in a material is its

A

crystal structure. A regular, repeating internal arrangement of atoms in a material is its crystal structure.

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9
Q

A quantity of stones of similar or mixed qualities, from a single mine or from various sources, offered for sale together is called a

A

parcel. Quantities of stones are commonly sold in parcels

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10
Q

Which trade term describes a mixture of gem qualities that represents unsorted production from a particular mine?

A

mine run

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11
Q

A natural, inorganic substance with a characteristic chemical composition and usually characteristic crystal structure is a

A

Minerals are natural, inorganic substances with a characteristic chemical composition and usually a characteristic crystal structure

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12
Q

A substance that consists of atoms of only one kind is a

A

A chemical element is a substance that consists of only one kind of atom.

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13
Q

A broad gem category based on chemical composition and crystal structure is a

A

species

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14
Q

Rocks altered by heat and pressure are

A

metamorphic. The heat and pressure of metamorphic processes transform rocks into new rocks

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15
Q

A deposit where gems are found in the rocks where they formed is called

A

primary

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16
Q

Which is a deposit where gems eroded from the source rock and remained in place nearby?

A

Eluvial deposits are a type of secondary deposit in which the gems are eroded from the source rock but not transported as they are in alluvial deposits

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17
Q

Atoms in a gem that are not part of its essential chemical composition are

A

Trace elements are trapped in a growing crystal, but they’re not necessary for the crystal’s growth, and they’re not part of its essential chemical composition

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18
Q

A unit cell defines a mineral’s

A

basic identity. The unit cell is the smallest group of atoms with the same chemical composition and crystal structure as the mineral. The unit cell is the mineral’s “signature”—its basic identity

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19
Q

Which type of twinning looks as if two crystal halves are mirror images?

A

contact. The two crystal halves of contact twins look like mirror images of each other. This is common in spinel

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20
Q

Which aggregate’s crystals are visible only under very high magnification?

A

cryptocrystalline. Detecting the small crystals that compose cryptocrystalline aggregates requires magnification that is beyond the power of standard gemological microscopes.

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21
Q

Which type of twinning is caused by environmental change after the gem forms?

A

Polysynthetic or lamellar twinning is a type of secondary twinning that occurs after the gem has formed when the rocks it formed in are altered by pressure from metamorphism.

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22
Q

How heavy an object is in relation to its size is called its

A

density. Some minerals are made of heavier elements than others, or have atoms that are closer together.

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23
Q

When a gem’s crystal structure splits light into two rays that each travel at a slightly different speed and direction, it’s called

A

double refraction. Most colored stones are doubly refractive, and their crystal structure splits light into two rays that each travel at a slightly different speed and direction

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24
Q

The pattern of dark vertical lines or bands shown by certain gems when viewed through a spectroscope is called

A

absorption spectrum. The spectroscope can show a characteristic pattern of dark lines and bands known as an absorption spectrum

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25
Q

The process where electrons that selectively absorb light are passed back and forth between neighboring impurity ions is known as

A

Charge transfer occurs when electrons that selectively absorb light are passed back and forth between neighboring impurity ions

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26
Q

A gem colored by an element that is part of its basic chemistry is called

A

idiochromatic.

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27
Q

Adularescence is caused by

A

Light scattered by the internal structure of moonstone causes its adularescence

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28
Q

Which phenomenon is a broad color flash?

A

Labradorescence

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29
Q

Which process dissolves nutrients in chemicals to form synthetic crystals?

A

flux growth.Chemicals dissolve the nutrients needed to form synthetic crystals by the flux growth process

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30
Q

Synthetic opal is grown using microscopic silica spheres that are produced by

A

precipitation. The chemical process used to produce microscopic silica spheres for growing synthetic opal is called precipitation.

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31
Q

Which synthetic process developed rapidly due to laser research in the 1960s?

A

The pulling process was developed to meet the need for inclusion-free synthetic ruby in laser equipment.

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32
Q

Low cost and high volume characterize which process?

A

The flame-fusion process produces a large volume of synthetic gems at low cost

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33
Q

Which process uses a heating unit that passes over a rotating solid rod of chemicals until it forms a synthetic crystal?

A

floating zone. a chemical rod rotates as a heating unit passes over it. This causes the material in the rod to crystallize in “zones” that eventually transform the rod into a single crystal

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34
Q

Which synthetic process uses an autoclave?

A

Hydrothermal growth. steel autoclave container

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35
Q

The crucibles that work best for flux growth are made of

A

platinum. The chemicals used in the flux process are very corrosive. Platinum is highly resistant to corrosion and works best for this process

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36
Q

Quartz or topaz with a thin layer of gold deposited on the surface is known as

A

aqua aura

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37
Q

What is a Single Phase inclusion

A

Liquid Inclusion

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38
Q

A smooth, flat break in a gemstone parallel to planes of atomic weakness, caused by weak or fewer bonds between atoms, or both

A

Cleavage

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39
Q

A flat break in a gemstone caused by concentrated included minerals parallel to a twinning plane.

A

Parting

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40
Q

Any break in a gem other than cleavage or parting, not feather

A

Fracture

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41
Q

3 Types of Igneous Formation

A
  1. Volcanic
  2. Pegmatites
  3. Superheated Water/ Hydrothermal
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42
Q

3 types of Metamorphic Formation

A
  1. Regional Metamorphism
  2. Contact Metamorphism
  3. Metasomatic
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43
Q

2 types of Sedimatary Formation

A
  1. Gems formed by Water Near Earths Surface
  2. Geode Formation
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44
Q

Clarity enhancement is…

A

the practice of filling gem fractures with a variety of substances to increase transparency and improve color and overall appearance.

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45
Q

“Kashmir” aka Cornflower describes sapphires that have a _______ blue to _______ blue hue, with moderately strong to vivid saturation and medium-dark tone. Minute
inclusions can give the gems a velvety appearance and desirable softness,
and also intensify their color.

A

violetish, pure

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46
Q

“Burmese” describes sapphires with a slightly________ blue to blue hue. Their
blue can be more intense and saturated than Kashmir sapphires. ________ under
incandescent light

A

violetish, inky

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47
Q

“Ceylon” and “Sri Lankan” refer to sapphires that generally have a
violetish blue to blue hue, with slightly_______ to strong saturation and
light to medium-light tone. The light tone means more light returns to the
viewer’s eyes, so these sapphires tend to be more _______

A

grayish, brilliant

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48
Q

________________ is the most common sapphire synthesis method

A

Flame fusion

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49
Q

Variations in conditions and coloring agents that occur during crystal growth can result in color _____________

A

zoning

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50
Q

In practice, what GIA Colored Stone Grading TONE levels apply to transparent colored stones?

A

TONE 2-8

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51
Q

The first impression of an object’s basic color is its

A

hue

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52
Q

When a singly refractive stone shows a second color face-up, this is called

A

light reflected within the stone interact with light transmitted through it

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53
Q

Extinction results from ________ _________, while shallow ones typically cause _________

A

deep pavilion, windows

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54
Q

Removing heavily included sections from gemstone rough by carefully tapping it with a small hammer is known as

A

cobbing

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55
Q

When viewed face-up, a stone with more than 75 percent brilliance is considered to have

A

excellent proportions

60 and 75 percent very good.
40 and 60 percent pretty good
25 and 40 percent fair
25 less poor

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56
Q

Which type of rough is usually faceted?

A

Transparent

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57
Q

A carved design that projects slightly from a flat or curved surface is called a(n)

A

cameo

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58
Q

Which cutting stage has the greatest impact on the value of the finished gem?

A

preforming

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59
Q

Important factors in evaluating a faceted gem’s proportions are its _______ and_________ depths, the________ of its profile, and its face-up outline

A

crown, pavilion, symmetry

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60
Q

____________ gems are the most likely to undergo cobbing

A

Lower-cost/ commercial quality

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61
Q

Rough that’s ground to the approximate shape of the finished stone is called

A

preform

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62
Q

An angular, hollow space that resembles a mineral inclusion is called a

A

Negative crystals are angular hollow spaces that resemble mineral inclusions

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63
Q

Fingerprints are

A

partially healed fracture planes.

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64
Q

The five factors that determine an inclusion’s impact on a gem’s value are

A

nature, size, number, position, and relief

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65
Q

Growth zoning in a colored stone is evidence of

A

crystal growth

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66
Q

In which of the following colored stone clarity grades do the definitions vary for each clarity type?

A

Moderately included

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67
Q

The clarity differences in definition between the________ included and___________ included grades of each clarity type are especially important. The distinctions between them
might seem subtle, but they can make a considerable difference in value

A

slightly, moderately

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68
Q

What category of colored stone is often sold per piece?

A

small, calibrated amethyst, peridot, garnet, citrine, and fire opal by the piece. Per-piece pricing for small, inexpensive gems helps commercial jewelry manufacturers track their expenses.

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69
Q

A gem’s price divided by its carat weight is called

A

per-carat price

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70
Q

Individual stone prices are referred to as

A

Unit price

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71
Q

How many points are in a metric carat?

A

100

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72
Q

Sieves are most useful for sorting round gems with diameters _________ and below

A

3mm

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73
Q

A metric carat equals _________ grams

A

.20

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74
Q

Most colored stones are sold by __________

A

weight

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75
Q

__________typically have the highest per-carat value of all fancy sapphires

A

Padparadschas

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76
Q

The finest yellow sapphire is yellow to_______ yellow, with medium tone and vivid
saturation.

A

orangy

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77
Q

Orange sapphires range from yellowish orange to reddish orange in light to dark tones and all degrees of saturation. The finest orange sapphires are strongly________-orange with medium tone and vivid saturation

A

red

78
Q

Green sapphire results from a mixture of two different color-causing mechanisms: yellow, caused by_______, and blue, caused by an iron and titanium intervalence charge transfer.

A

iron

79
Q

The least expensive and perhaps most commonly seen star sapphires are
black stars from _______ and __________

A

Thailand and Australia

80
Q

Generally, gem weight is stated to the nearest

A

hundredth of a carat

81
Q

The trade term “____________” is often used to describe emeralds that are slightly darker and more bluish than “Colombian” emeralds

A

Zambian

82
Q

The organ that lines the mollusk’s shell, encloses its soft body, and contains the cells that form pearl sacs and secrete nacre

A

mantle

83
Q

The natural substance produced by pearl-bearing mollusks to make pearls.

A

Nacre

84
Q

A crystallized form of calcium carbonate found in nacre

A

aragonite

85
Q

The organic “glue” in nacre that holds aragonite platelets together

A

Conchiolin

86
Q

The nacreous layer inside a pearl-bearing mollusk’s shell

A

Mother-of-pearl

87
Q

Optical phenomenon created in some non-nacreous pearls when intersecting groups of crystals interact with light

A

flame structure

88
Q

A bead used as the core of a cultured pearl, usually made from a freshwater mussel shell

A

bead nucleus

89
Q

A bead used as the core of a cultured pearl, usually made from a freshwater mussel shell

A

Mantle-tissue piece

90
Q

Tissue that encloses an implanted bead nucleus and mantle tissue piece, or the piece alone, and secretes nacre to form a cultured pearl

A

Pearl sac

91
Q

Common name for the Pinctada fucata oyster and the natural or cultured pearls it produces

A

Akoya

92
Q

Tahitian Peacock is the trade term for a dark green-gray to blue-gray bodycolor with______ to ________ overtones. It’s often the most highly valued color

A

pink to purple

93
Q

A three-step freshwater cultivation process involving a series of distinct growth periods

A

Coin-bead/spherical-bead (CBSB) production

94
Q

Product that results when a pearl-bearing mollusk is returned to the water after the first harvest

A

Second-generation cultured pearl

95
Q

A number of similar cultured pearl strands bundled together

A

Hank

96
Q

A company that prepares cultured pearls for the market

A

Processor

97
Q

assembled cultured blister pearl.
Composed of a nacre dome, filler, and a mother-of-pearl backing

A

Mabé

98
Q

Golden pearl—Strong_______ yellow to________ yellow South Sea cultured pearls

A

greenish, orangy

99
Q

Pistachio pearl—Tahitian cultured pearls with a_________ green to_________ yellow bodycolor

A

yellowish, greenish

100
Q

Luster in pearls is caused by light traveling through translucent layers of nacre and reflecting back to the eye. The nacre’s thickness, its degree of translucence, and the arrangement of the overlapping nacre layers all
contribute to luster

A

Lustre

101
Q

Trade name for the finest quality, semitransparent jadeite with even, vivid green coloration

A

Imperial

102
Q

An uneven distribution of color against a contrasting background

A

Mottling

103
Q

Gemstone jewelry carved entirely from a single piece of rough

A

Hololith

104
Q

Spots of color near the surface of a jadeite boulder, where the skin is thin enough to allow color to show through

A

Show points

105
Q

A trade name for top-quality white nephrite

A

Mutton-fat jade

106
Q

Rough nephrite extracted directly from primary deposits

A

Mountain jade

107
Q

Opal that lacks play-of color

A

Potch opal, non-precious

108
Q

In this model, seasonal rainwater soaks the dry ground in opal’s arid source areas. The water dissolves the silica as it trickles downward and deposits it in voids and cracks in the rocks. Much of the water evaporates during the dry season, leaving a solid hydrous silica deposit behind. This hydrous silica deposit is opal.

A

The Weathering Theory

109
Q

A gem material’s host rock, which sometimes becomes part of the finished gem ie. boulder opal

A

Matrix

110
Q

An opal’s bodycolor, independent of its play of- color

A

Background color

111
Q

A manmade glass opal imitation with scattered, tinsel like colored flakes that imitate play-of-color

A

Slocum Stone

112
Q

A cryptocrystalline quartz aggregate

A

Chalcedony

113
Q

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

A

Agate

114
Q

Transparent quartz, usually rock crystal, that contains eye-visible inclusions, often named
according to the type of inclusions it contains ie. Rutilated quartz, toumralinated quartz

A

Sagenitic quartz

115
Q

A type of sagenitic quartz containing needle-like rutile inclusions

A

Rutilated quartz

116
Q

A type of sagenitic quartz containing needle-like or rod-like tourmaline inclusions

A

Tourmalinated quartz

117
Q

Unlike most chatoyant gems, neither _______-eye nor__________-eye requires a curved surface to display chatoyancy

A

tiger’s, hawk’s

118
Q

A property of some crystals that causes them to generate an electrical charge when subjected to mechanical stress

A

Piezoelectricity

119
Q

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

A

Botryoidal

120
Q

A procedure that includes cleaning, buffing, and sometimes bleaching, done to make cultured pearls presentable and appealing, is called

A

Processing

121
Q

The matching level that describes a group of pearls with minor variations in uniformity is

A

Good
* Excellent—Pearls are uniform in appearance and drilled on center
* Very Good—Very minor variations in uniformity
* Good—Minor variations in uniformity
* Fair—Noticeable variations in uniformity
* Poor—Very noticeable variations in uniformity

122
Q

Play-of-color that’s seen only when light travels through an opal to the eye is called

A

contra luz

123
Q

Which treatment involves immersing opal in concentrated sulfuric acid?

A

sugar

124
Q

Who created the first marketable synthetic opal?

A

Pierre GILSON of Switzerland, synth emerald

125
Q

“Marabá” amethyst is often

A

uniform in color

126
Q

Tanavyte is a trade name for

A

purple synthetic YAG

127
Q

Nacre is composed primarily of

A

aragonite and conchiolin

128
Q

A trade term for hydrogrossular garnet is

A

Transvaal jade, african jade

129
Q

When the outline of an earlier growth phase is visible within a quartz crystal, this is called

A

the phantom effect

130
Q

All quartz varieties can be divided into three broad categories based on crystal size:_________ crystal, microcrystalline aggregates, and cryptocrystalline aggregates

A

single

131
Q

Which stone is known as the cross stone?

A

Chiastolite andalusite

132
Q

A widely used trade term for gem-quality topaz of medium reddish orange to orange-red color

A

Imperial topaz
Chromium causes natural pink, red, and violet-to-purple colors in topaz.
Color centers cause yellow, brown, and blue.
If both chromium and color centers are present, the topaz will be orange

133
Q

Because of its___________, topaz requires special care in cutting, polishing, mounting, and wear

A

basal cleavage, parallel to base

134
Q

A trade term for orange-to-yellow and brown topaz

A

Precious topaz/ sherry

135
Q

Topaz heat treated to pink or irradiated and heated for blue are

A

stable

136
Q

The finest aquamarines are a moderately strong, ___________-__________ blue to slightly greenish blue

A

medium-dark

137
Q

Gems that show color zoning with two or more colors

A

Parti-colored

138
Q

A tourmaline, usually elbaite, with color zoning made up of a pink central zone
surrounded by a green overgrowth

A

Watermelon tourmaline

139
Q

Trade term for a vibrant green tourmaline that’s colored by traces of vanadium, chromium, or both

A

Chrome tourmaline

140
Q

Trade name for pink to red elbaite tourmaline

A

Rubellite

141
Q

Trade term for rare, expensive, vibrant green to blue or violet elbaite tourmaline, originally found only in Brazil’s Paraíba state

A

Paraíba tourmaline

142
Q

Trade term for blue tourmaline.

A

indicolite

143
Q

A mineral that’s been broken down from a crystalline to a partly amorphous state by
emanations from radioactive impurities. In LOW zircon, green

A

Metamict

144
Q

A cabochon with a curved, undercut bottom, designed to lighten the tone of the gem material

A

Hollowback

145
Q

Substitution of one chemical element for another in the crystal structure of a mineral

A

Isomorphous replacement

146
Q

A trade term for polymer-impregnated turquoise

A

Stabilized turquoise

147
Q

A turquoise imitation made of a mixture of powdered minerals, dyed and bonded with plastic or epoxy resin

A

Reconstructed turquoise

148
Q

Trade term for a highly prized, vivid blue adularescence displayed by the finest moonstone

A

Blue sheen

149
Q

Tiny tension cracks in moonstone that interfere with adularescence and reduce value.

A

Centipedes

150
Q

An imitation of aventurine feldspar made of glass that contains small copper crystals

A

Goldstone

151
Q

Horsetail inclusions are found in

A

Demantoid

152
Q

The trade term malaya is used for a pinkish orange garnet that’s a mixture of

A

pyrope, spessartine, and almandine

153
Q

A treatment that makes turquoise less porous without the use of polymers and improves its ability to take a good polish is

A

Zachary method

154
Q

polymer-impregnated turquoise is called

A

Stabilized turquoise

155
Q

Rainbow moonstone is a trade term for a type of

A

It’s a variety of labradorite, a plagioclase-series feldspar

156
Q

Immature amber is known as

A

Copal

157
Q

a Maori name for abalone shell

A

Paua

158
Q

___________A laboratory creation with essentially the same chemical composition, crystal structure, and properties as its natural counterpart
___________Any material that looks like a natural gem and is used in its place.

A

Synthetic gem vs Imitation gem

159
Q

A synthetic-crystal growth method in which the chemical mixture is melted, then recrystallized

A

Melt process.
Ie Flame fusion, pulling, boule, floating zone

160
Q

A growth method in which the synthetic crystal grows from a dissolved chemical mixture,
sometimes at high temperature and pressure

A

Solution process
ie. flux growth, hydrothermal

161
Q

A process in which powdered chemicals are dropped through a high-temperature flame
onto a rotating pedestal to produce a synthetic crystal.

A

Flame fusion. Auguste Vernuiel
$5 or less

162
Q

A process in which the synthetic crystal grows from a seed that is dipped into a chemical melt, then pulled away as it gathers material

A

Pulling, sapphire synthesis
$5 x 10

laser research

163
Q

A melt process where a heating unit passes over a rotating solid rod of chemicals until it forms a synthetic crystal

A

Floating zone. 1953,
responding to a need for high-quality silicon semiconductors

164
Q

A synthetic-crystal growth method that uses cooling pipes around an interior of melted
chemical ingredients

A

Skull melt. high-temperature technique that produces CZ

165
Q

A process in which nutrients dissolve in heated chemicals, then cool to form synthetic crystals

A

Flux growth: crucible, seed crystal
emerald, rubies, sapphires, alexandrites, and spinels
$100/ct

166
Q

A process in which nutrients dissolve in a water solution at high temperature and pressure, then cool to form synthetic crystals.

A

Hydrothermal growth. steel autoclave, seed cystal
quartz
$100/ct

167
Q

A synthetic crystal growth method that starts without a seed crystal

A

Spontaneous nucleation

168
Q

_________________Two or more separate pieces of material joined to form a unit
_________________A single assembled stone made from three separate pieces of material fused or cemented together, or from two pieces and a colored cement layer

A

Assembled stone
Triplet

169
Q

Direction of single refraction in a doubly refractive gem

A

Optic axis, no double refraction direction

170
Q

Continued emission of visible light
after UV or X-ray stimulation stops

A

Phosphorescence

171
Q

A process where two transition elements with different valences exchange electrons to selectively absorb light

A

Intervalence charge transfer

172
Q

A small defect in the crystal structure of a material that can absorb light and give rise to a color

A

Color center

173
Q

A special kind of interference phenomenon that produces patches of pure spectral colors ie opal, labradorite

A

Diffraction

174
Q

Localized changes caused by an igneous intrusion that takes place where the magma meets the surrounding rock

A

Contact metamorphism

175
Q

An igneous rock typically formed from cooling, once-molten granite that follows fractures in its surrounding rock
igneous rock - Rock formed by the crystallization of molten material

A

Pegmatite

176
Q

A deposit where gems are eroded from the source rock but remain in place close to the source

A

Eluvial deposit

177
Q

A type of metamorphism where chemical changes in the minerals and rocks result from
the introduction of material from external sources, often as hydrothermal solutions

A

Metasomatism

178
Q

Changes in rock type and minerals over a wide area, caused by heat and pressure of large-scale geological events

A

Regional metamorphism

179
Q

Rock produced from the eroded and weathered remains of existing rocks

A

Sedimentary rock

180
Q

Large mass of igneous rock that crystallizes underground without reaching the surface

A

Intrusion

181
Q

Crystallization of minerals from a gas

A

Pneumatolysis

182
Q

___________ A family of gems from several closely related mineral species
___________A broad gem category based on chemical composition and crystal structure
___________A subcategory of species, based on color, transparency, or phenomenon

A

Group
Species
Variety

183
Q

Impurities and defects provide additional energy levels in some gems’ band gaps. Electrons can more easily make transitions between these energy levels within the band gap by selectively absorbing visible light and producing color

A

Band theory

184
Q

Gem color is produced when electrons of individual transition
element ions selectively absorb some wavelengths of visible
light

A

Transition element

185
Q

structure Squat and flat, like many corundum crystals

A

Tabular

186
Q

structure Columnar, with 3, 4, 6, 8, or 12 parallel faces. ie aquamarine and tourmaline crystals

A

Prism or prismatic

187
Q

structure Well formed, with sharp crystal faces, like most gems from pegmatite pockets

A

Euhedral

188
Q

structure Lacking obvious crystal faces, like many gems that have been tumbled in rivers

A

Anhedral

189
Q

structure Horizontal (quartz, corundum) or vertical (tourmaline, topaz) growth markings on a crystal

A

Striations

190
Q

structure Shape with equal triangular faces that meet ina point

A

Pyramid

191
Q

structure Shape with two pyramids back-to-back. Seen in sapphires, for example

A

Bipyramid

192
Q
A

Colored Gems (2 decks)

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