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
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
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.
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.
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.
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
7
Q
A rock must
A
Rocks are composed of masses of one or more kinds of mineral crystals
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.
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
10
Q
Which trade term describes a mixture of gem qualities that represents unsorted production from a particular mine?
A
mine run
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
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.
13
Q
A broad gem category based on chemical composition and crystal structure is a
A
species
14
Q
Rocks altered by heat and pressure are
A
metamorphic. The heat and pressure of metamorphic processes transform rocks into new rocks
15
Q
A deposit where gems are found in the rocks where they formed is called
A
primary
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
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
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
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
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.
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.
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.
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
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
25
The process where electrons that selectively absorb light are passed back and forth between neighboring impurity ions is known as
Charge transfer occurs when electrons that selectively absorb light are passed back and forth between neighboring impurity ions
26
A gem colored by an element that is part of its basic chemistry is called
idiochromatic.
27
Adularescence is caused by
Light scattered by the internal structure of moonstone causes its adularescence
28
Which phenomenon is a broad color flash?
Labradorescence
29
Which process dissolves nutrients in chemicals to form synthetic crystals?
flux growth.Chemicals dissolve the nutrients needed to form synthetic crystals by the flux growth process
30
Synthetic opal is grown using microscopic silica spheres that are produced by
precipitation. The chemical process used to produce microscopic silica spheres for growing synthetic opal is called precipitation.
31
Which synthetic process developed rapidly due to laser research in the 1960s?
The pulling process was developed to meet the need for inclusion-free synthetic ruby in laser equipment.
32
Low cost and high volume characterize which process?
The flame-fusion process produces a large volume of synthetic gems at low cost
33
Which process uses a heating unit that passes over a rotating solid rod of chemicals until it forms a synthetic crystal?
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
34
Which synthetic process uses an autoclave?
Hydrothermal growth. steel autoclave container
35
The crucibles that work best for flux growth are made of
platinum. The chemicals used in the flux process are very corrosive. Platinum is highly resistant to corrosion and works best for this process
36
Quartz or topaz with a thin layer of gold deposited on the surface is known as
aqua aura
37
What is a Single Phase inclusion
Liquid Inclusion
38
A smooth, flat break in a gemstone parallel to planes of atomic weakness, caused by weak or fewer bonds between atoms, or both
Cleavage
39
A flat break in a gemstone caused by concentrated included minerals parallel to a twinning plane.
Parting
40
Any break in a gem other than cleavage or parting, not feather
Fracture
41
3 Types of Igneous Formation
1. Volcanic
2. Pegmatites
3. Superheated Water/ Hydrothermal
42
3 types of Metamorphic Formation
1. Regional Metamorphism
2. Contact Metamorphism
3. Metasomatic
43
2 types of Sedimatary Formation
1. Gems formed by Water Near Earths Surface
2. Geode Formation
44
Clarity enhancement is...
the practice of filling gem fractures with a variety of substances to increase transparency and improve color and overall appearance.
45
“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.
violetish, pure
46
“Burmese” describes sapphires with a slightly________ blue to blue hue. Their
blue can be more intense and saturated than Kashmir sapphires. ________ under
incandescent light
violetish, inky
47
“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 _______
grayish, brilliant
48
________________ is the most common sapphire synthesis method
Flame fusion
49
Variations in conditions and coloring agents that occur during crystal growth can result in color _____________
zoning
50
In practice, what GIA Colored Stone Grading TONE levels apply to transparent colored stones?
TONE 2-8
51
The first impression of an object’s basic color is its
hue
52
When a singly refractive stone shows a second color face-up, this is called
light reflected within the stone interact with light transmitted through it
53
Extinction results from ________ _________, while shallow ones typically cause _________
deep pavilion, windows
54
Removing heavily included sections from gemstone rough by carefully tapping it with a small hammer is known as
cobbing
55
When viewed face-up, a stone with more than 75 percent brilliance is considered to have
excellent proportions
60 and 75 percent **very good.**
40 and 60 percent **pretty good**
25 and 40 percent **fair**
25 less **poor**
56
Which type of rough is usually faceted?
Transparent
57
A carved design that projects slightly from a flat or curved surface is called a(n)
cameo
58
Which cutting stage has the greatest impact on the value of the finished gem?
preforming
59
Important factors in evaluating a faceted gem’s proportions are its _______ and_________ depths, the________ of its profile, and its face-up outline
crown, pavilion, symmetry
60
____________ gems are the most likely to undergo cobbing
Lower-cost/ commercial quality
61
Rough that’s ground to the approximate shape of the finished stone is called
preform
62
An angular, hollow space that resembles a mineral inclusion is called a
Negative crystals are angular hollow spaces that resemble mineral inclusions
63
Fingerprints are
partially healed fracture planes.
64
The five factors that determine an inclusion’s impact on a gem’s value are
nature, size, number, position, and relief
65
Growth zoning in a colored stone is evidence of
crystal growth
66
In which of the following colored stone clarity grades do the definitions vary for each clarity type?
Moderately included
67
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
slightly, moderately
68
What category of colored stone is often sold per piece?
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.
69
A gem’s price divided by its carat weight is called
per-carat price
70
Individual stone prices are referred to as
Unit price
71
How many points are in a metric carat?
100
72
Sieves are most useful for sorting round gems with diameters _________ and below
3mm
73
A metric carat equals _________ grams
.20
74
Most colored stones are sold by __________
weight
75
__________typically have the highest per-carat value of all fancy sapphires
Padparadschas
76
The finest yellow sapphire is yellow to_______ yellow, with medium tone and vivid
saturation.
orangy
77
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
red
78
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.
iron
79
The least expensive and perhaps most commonly seen star sapphires are
black stars from _______ and __________
Thailand and Australia
80
Generally, gem weight is stated to the nearest
hundredth of a carat
81
The trade term “____________” is often used to describe emeralds that are slightly darker and more bluish than “Colombian” emeralds
Zambian
82
The organ that lines the mollusk’s shell, encloses its soft body, and contains the cells that form pearl sacs and secrete nacre
mantle
83
The natural substance produced by pearl-bearing mollusks to make pearls.
Nacre
84
A crystallized form of calcium carbonate found in nacre
aragonite
85
The organic “glue” in nacre that holds aragonite platelets together
Conchiolin
86
The nacreous layer inside a pearl-bearing mollusk’s shell
Mother-of-pearl
87
Optical phenomenon created in some non-nacreous pearls when intersecting groups of crystals interact with light
flame structure
88
A bead used as the core of a cultured pearl, usually made from a freshwater mussel shell
bead nucleus
89
A bead used as the core of a cultured pearl, usually made from a freshwater mussel shell
Mantle-tissue piece
90
Tissue that encloses an implanted bead nucleus and mantle tissue piece, or the piece alone, and secretes nacre to form a cultured pearl
Pearl sac
91
Common name for the Pinctada fucata oyster and the natural or cultured pearls it produces
Akoya
92
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
pink to purple
93
A three-step freshwater cultivation process involving a series of distinct growth periods
Coin-bead/spherical-bead (CBSB) production
94
Product that results when a pearl-bearing mollusk is returned to the water after the first harvest
Second-generation cultured pearl
95
A number of similar cultured pearl strands bundled together
Hank
96
A company that prepares cultured pearls for the market
Processor
97
assembled cultured blister pearl.
Composed of a nacre dome, filler, and a mother-of-pearl backing
Mabé
98
Golden pearl—Strong_______ yellow to________ yellow South Sea cultured pearls
greenish, orangy
99
Pistachio pearl—Tahitian cultured pearls with a_________ green to_________ yellow bodycolor
yellowish, greenish
100
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
Lustre
101
Trade name for the finest quality, semitransparent jadeite with even, vivid green coloration
Imperial
102
An uneven distribution of color against a contrasting background
Mottling
103
Gemstone jewelry carved entirely from a single piece of rough
Hololith
104
Spots of color near the surface of a jadeite boulder, where the skin is thin enough to allow color to show through
Show points
105
A trade name for top-quality white nephrite
Mutton-fat jade
106
Rough nephrite extracted directly from primary deposits
Mountain jade
107
Opal that lacks play-of color
Potch opal, non-precious
108
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.
The Weathering Theory
109
A gem material’s host rock, which sometimes becomes part of the finished gem ie. boulder opal
Matrix
110
An opal’s bodycolor, independent of its play of- color
Background color
111
A manmade glass opal imitation with scattered, tinsel like colored flakes that imitate play-of-color
Slocum Stone
112
A cryptocrystalline quartz aggregate
Chalcedony
113
Chalcedony with curved or angular bands or layers that differ in color and transparency.
Agate
114
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
Sagenitic quartz
115
A type of sagenitic quartz containing needle-like rutile inclusions
Rutilated quartz
116
A type of sagenitic quartz containing needle-like or rod-like tourmaline inclusions
Tourmalinated quartz
117
Unlike most chatoyant gems, neither _______-eye nor__________-eye requires a curved surface to display chatoyancy
tiger’s, hawk’s
118
A property of some crystals that causes them to generate an electrical charge when subjected to mechanical stress
Piezoelectricity
119
A crystal growth habit in chalcedon with a bumpy appearance similar to a bunch of grapes
Botryoidal
120
A procedure that includes cleaning, buffing, and sometimes bleaching, done to make cultured pearls presentable and appealing, is called
Processing
121
The matching level that describes a group of pearls with minor variations in uniformity is
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
Play-of-color that’s seen only when light travels through an opal to the eye is called
contra luz
123
Which treatment involves immersing opal in concentrated sulfuric acid?
sugar
124
Who created the first marketable synthetic opal?
Pierre GILSON of Switzerland, synth emerald
125
“Marabá” amethyst is often
uniform in color
126
Tanavyte is a trade name for
purple synthetic YAG
127
Nacre is composed primarily of
aragonite and conchiolin
128
A trade term for hydrogrossular garnet is
Transvaal jade, african jade
129
When the outline of an earlier growth phase is visible within a quartz crystal, this is called
the phantom effect
130
All quartz varieties can be divided into three broad categories based on crystal size:_________ crystal, microcrystalline aggregates, and cryptocrystalline aggregates
single
131
Which stone is known as the cross stone?
Chiastolite andalusite
132
A widely used trade term for gem-quality topaz of medium reddish orange to orange-red color
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
Because of its___________, topaz requires special care in cutting, polishing, mounting, and wear
basal cleavage, parallel to base
134
A trade term for orange-to-yellow and brown topaz
Precious topaz/ sherry
135
Topaz heat treated to pink or irradiated and heated for blue are
stable
136
The finest aquamarines are a moderately strong, ___________-__________ blue to slightly greenish blue
medium-dark
137
Gems that show color zoning with two or more colors
Parti-colored
138
A tourmaline, usually elbaite, with color zoning made up of a pink central zone
surrounded by a green overgrowth
Watermelon tourmaline
139
Trade term for a vibrant green tourmaline that’s colored by traces of vanadium, chromium, or both
Chrome tourmaline
140
Trade name for pink to red elbaite tourmaline
Rubellite
141
Trade term for rare, expensive, vibrant green to blue or violet elbaite tourmaline, originally found only in Brazil’s Paraíba state
Paraíba tourmaline
142
Trade term for blue tourmaline.
indicolite
143
A mineral that’s been broken down from a crystalline to a partly amorphous state by
emanations from radioactive impurities. In LOW zircon, green
Metamict
144
A cabochon with a curved, undercut bottom, designed to lighten the tone of the gem material
Hollowback
145
Substitution of one chemical element for another in the crystal structure of a mineral
Isomorphous replacement
146
A trade term for polymer-impregnated turquoise
Stabilized turquoise
147
A turquoise imitation made of a mixture of powdered minerals, dyed and bonded with plastic or epoxy resin
Reconstructed turquoise
148
Trade term for a highly prized, vivid blue adularescence displayed by the finest moonstone
Blue sheen
149
Tiny tension cracks in moonstone that interfere with adularescence and reduce value.
Centipedes
150
An imitation of aventurine feldspar made of glass that contains small copper crystals
Goldstone
151
Horsetail inclusions are found in
Demantoid
152
The trade term malaya is used for a pinkish orange garnet that’s a mixture of
pyrope, spessartine, and almandine
153
A treatment that makes turquoise less porous without the use of polymers and improves its ability to take a good polish is
Zachary method
154
polymer-impregnated turquoise is called
Stabilized turquoise
155
Rainbow moonstone is a trade term for a type of
It’s a variety of labradorite, a plagioclase-series feldspar
156
Immature amber is known as
Copal
157
a Maori name for abalone shell
Paua
158
___________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.
Synthetic gem vs Imitation gem
159
A synthetic-crystal growth method in which the chemical mixture is melted, then recrystallized
Melt process.
Ie Flame fusion, pulling, boule, floating zone
160
A growth method in which the synthetic crystal grows from a dissolved chemical mixture,
sometimes at high temperature and pressure
Solution process
ie. flux growth, hydrothermal
161
A process in which powdered chemicals are dropped through a high-temperature flame
onto a rotating pedestal to produce a synthetic crystal.
Flame fusion. Auguste Vernuiel
$5 or less
162
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
Pulling, sapphire synthesis
$5 x 10
| laser research
163
A melt process where a heating unit passes over a rotating solid rod of chemicals until it forms a synthetic crystal
Floating zone. 1953,
responding to a need for high-quality silicon semiconductors
164
A synthetic-crystal growth method that uses cooling pipes around an interior of melted
chemical ingredients
Skull melt. high-temperature technique that produces CZ
165
A process in which nutrients dissolve in heated chemicals, then cool to form synthetic crystals
Flux growth: crucible, seed crystal
emerald, rubies, sapphires, alexandrites, and spinels
$100/ct
166
A process in which nutrients dissolve in a water solution at high temperature and pressure, then cool to form synthetic crystals.
Hydrothermal growth. steel autoclave, seed cystal
quartz
$100/ct
167
A synthetic crystal growth method that starts without a seed crystal
Spontaneous nucleation
168
_________________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
Assembled stone
Triplet
169
Direction of single refraction in a doubly refractive gem
Optic axis, no double refraction direction
170
Continued emission of visible light
after UV or X-ray stimulation stops
Phosphorescence
171
A process where two transition elements with different valences exchange electrons to selectively absorb light
Intervalence charge transfer
172
A small defect in the crystal structure of a material that can absorb light and give rise to a color
Color center
173
A special kind of interference phenomenon that produces patches of pure spectral colors ie opal, labradorite
Diffraction
174
Localized changes caused by an igneous intrusion that takes place where the magma meets the surrounding rock
Contact metamorphism
175
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
Pegmatite
176
A deposit where gems are eroded from the source rock but remain in place close to the source
Eluvial deposit
177
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
Metasomatism
178
Changes in rock type and minerals over a wide area, caused by heat and pressure of large-scale geological events
Regional metamorphism
179
Rock produced from the eroded and weathered remains of existing rocks
Sedimentary rock
180
Large mass of igneous rock that crystallizes underground without reaching the surface
Intrusion
181
Crystallization of minerals from a gas
Pneumatolysis
182
___________ 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
Group
Species
Variety
183
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
Band theory
184
Gem color is produced when electrons of individual transition
element ions selectively absorb some wavelengths of visible
light
Transition element
185
structure Squat and flat, like many corundum crystals
Tabular
186
structure Columnar, with 3, 4, 6, 8, or 12 parallel faces. ie aquamarine and tourmaline crystals
Prism or prismatic
187
structure Well formed, with sharp crystal faces, like most gems from pegmatite pockets
Euhedral
188
structure Lacking obvious crystal faces, like many gems that have been tumbled in rivers
Anhedral
189
structure Horizontal (quartz, corundum) or vertical (tourmaline, topaz) growth markings on a crystal
Striations
190
structure Shape with equal triangular faces that meet ina point
Pyramid
191
structure Shape with two pyramids back-to-back. Seen in sapphires, for example
Bipyramid
192
