GIA Ch 1 - 27 ALL Flashcards
1
Q
What gemstone’s consumer confidence was reduced in the 1990s due to media attention regarding treatments?
A
emerald.
Consumer confidence in emerald was reduced in the 1990s due to media attention regarding treatments.
2
Q
Who primarily mines many colored stones?
A
independent miners using small-scale mining methods.
Independent miners using small-scale mining methods mine many colored stones.
3
Q
What are most gems classified as?
A
minerals.
Most gems are minerals.
4
Q
Which country is the world’s largest gem-consuming market?
A
the United States.
The United States is the world’s largest gem-consuming market, followed by China.
5
Q
What is a broad gem category based on chemical composition and crystal structure called?
A
gem species.
A broad gem category based on chemical composition and crystal structure is a gem species.
6
Q
What is a substance that consists of atoms of only one kind?
A
chemical element.
A chemical element is a substance that consists of only one kind of atom.
7
Q
To be classified as a gem, a mineral must be beautiful, durable, and _______.
A
rare.
To be a gem, a mineral must be beautiful, durable, and rare.
8
Q
What is a natural, inorganic substance with a characteristic chemical composition and usually characteristic crystal structure?
A
mineral.
Minerals are natural, inorganic substances with a characteristic chemical composition and usually a characteristic crystal structure.
9
Q
To which group does almandine belong?
A
Garnet.
Almandine belongs to the garnet group.
10
Q
Which of the following is an organic gem?
A
Amber.
Amber is an organic gem.
11
Q
Example of a gem that is classified as amorphous?
A
Amber, Opal, Obsidian
Amber is an amorphous gem.
12
Q
What is a natural material made up of a mass of one or more kinds of mineral crystals?
A
rock.
Rocks are masses of one or more kinds of mineral crystals.
13
Q
What is an example of a gem variety?
A
Demantoid. Almandine. Pyrope. Tsavorite. Spessartine. Sapphire. Ruby. Aquamarine. Amethyst. Emerald. Citrine. Alexandrite. Moonstone. Sunstone. others
Demantoid is a variety of andradite garnet.
14
Q
What do you call a gem produced by, or derived from, a living organism?
A
organic.
Organic gems are derived from living organisms.
15
Q
Are synthetic gem materials considered minerals?
A
No.
Synthetic gem materials are not minerals because they’re grown in a laboratory rather than in the earth.
16
Q
Which gem can crystallize in volcanic rock from gases released by magma?
A
Red beryl and topaz
Both red beryl and topaz can crystallize from gases released by magma during the final cooling stages.
17
Q
Kunzite is most often found in association with which minerals?
A
Tourmaline and beryl
Tourmaline, beryl, and kunzite are all found in association with pegmatites.
18
Q
Emeralds are rarely found in placer deposits because they’re unable to withstand much _______.
A
abrasion
19
Q
Which type of deposit is usually the most profitable for colored stone mining?
A
Secondary
Erosion has done some of the work for miners of secondary deposits, making them more profitable than primary deposits.
20
Q
Rocks altered by heat and pressure are called _______.
A
metamorphic
21
Q
Which is a key locality for hydrothermal gems?
A
Ouro Preto, Brazil
Imperial topaz from Brazil and emeralds from Colombia are important hydrothermal gems.
22
Q
Myanmar’s famous Mogok ruby deposits were formed by _______ processes.
A
metamorphic
23
Q
Which is a deposit where gems eroded from the source rock and remained in place nearby?
A
Eluvial
Eluvial deposits are a type of secondary deposit where gems are eroded from the source rock but not transported.
24
Q
From granite, pegmatite gems get exotic elements like _______.
A
beryllium, boron, and lithium
25
Most of the gems in Tanzania’s Umba River Valley are found in _______ deposits.
placer
26
Which is a workable alluvial deposit of gem minerals with economic potential?
Placer
## Footnote
When an alluvial deposit shows economic potential, it is referred to as a placer.
27
Heat and pressure transform limestone into _______.
marble
28
name 3 gems formed by metamorphism?
Tanzanite, ruby, emerald, alexandrite, and tsavorite. garnet, sapphire, spinel, and kyanite.
## Footnote
The metamorphic rocks of East Africa produce tanzanite, ruby, emerald, alexandrite, and tsavorite.
29
A deposit where gems are found in the rocks where they formed is called _______.
primary
30
Most gemstones form in the _______.
continental crust
31
Which element causes red in ruby and green in emerald?
Chromium
## Footnote
Chromium is known for producing valuable colors in gems.
32
A unit cell defines a mineral’s _______.
basic identity
## Footnote
The unit cell is the smallest group of atoms with the same chemical composition and crystal structure.
33
Crystals that grow in a flux that is highly saturated with the necessary elements tend to be _______.
small
## Footnote
High saturation in the flux leads to the growth of many small crystals.
34
Many fashioned rubies have shallow proportions because they’re cut from _______.
flattened crystals
## Footnote
Understanding the rough shape of rubies helps buyers recognize why cut rubies often have shallow proportions.
35
How heavy an object is in relation to its size is called its _______.
density
## Footnote
Density depends on the elements in the mineral and their atomic arrangement.
36
Which type of twinning looks as if two crystal halves are mirror images?
Contact
## Footnote
Contact twins are common in minerals like spinel.
37
Which gems are cryptocrystalline aggregates?
Chalcedony and turquoise
## Footnote
These gems consist of very tiny individual crystals.
38
Which is classified in the orthorhombic crystal system?
Topaz
## Footnote
Topaz's unit cell structure places it in the orthorhombic system.
39
Rough spinel often occurs as _______.
twinned crystals
## Footnote
Spinel is commonly found as contact twins.
40
The trace elements that cause corundum’s blue are _______.
iron and titanium
## Footnote
These elements alter corundum's chemical composition to create a blue color.
41
Atoms in a gem that are not part of its essential chemical composition are called _______.
trace elements
## Footnote
Trace elements are not necessary for crystal growth.
42
Needles of actinolite found in emerald are classified as _______.
inclusions
## Footnote
Inclusions can include various characteristics, such as crystals or needles.
43
A two-phase inclusion is a cavity in a gem that’s typically filled with _______.
a liquid and a gas
## Footnote
This type of inclusion often consists of a liquid phase and a gas bubble.
44
Which aggregate’s crystals are visible only under very high magnification?
Cryptocrystalline
## Footnote
Standard gemological microscopes cannot detect the small crystals in cryptocrystalline aggregates.
45
Which type of twinning is caused by environmental change after the gem forms?
Polysynthetic
## Footnote
This twinning occurs when rocks undergo metamorphism after gem formation.
46
The pattern of dark vertical lines or bands shown by certain gems when viewed through a spectroscope is called
absorption spectrum
## Footnote
The spectroscope can show a characteristic pattern of dark lines and bands known as an absorption spectrum.
47
Which transition element causes a greater variety of gem colors than any other?
Iron
## Footnote
Iron causes a wide variety of colors in gems.
48
In many blue sapphires, the intervalence charge transfer that causes the color is between
iron and titanium
## Footnote
The intervalence charge transfer between iron and titanium causes the color in many blue sapphires.
49
The process where electrons that selectively absorb light are passed back and forth between neighboring impurity ions is known as
charge transfer
## Footnote
Charge transfer occurs when electrons that selectively absorb light are passed back and forth between neighboring impurity ions.
50
Which gem can show three pleochroic colors?
Iolite
## Footnote
Like tanzanite and andalusite, iolite can show three pleochroic colors.
51
What is the only type of gem that can show pleochroism?
Doubly refractive
## Footnote
Only doubly refractive gems can show pleochroism.
52
A gem colored by an element that is part of its basic chemistry is called
idiochromatic
## Footnote
An idiochromatic gem is colored by an element that is part of the gem’s essential chemistry.
53
Which components of a transition element’s atoms can produce color in gems?
Electrons
## Footnote
Electrons are the components of a transition element’s atoms that produce color in gems.
54
Which element causes the color of both almandine and peridot?
Iron
## Footnote
Iron is the element that causes the red in almandine and the yellowish green in peridot.
55
Adularescence is caused by
scattering of light
## Footnote
Light scattered by the internal structure of moonstone causes its adularescence.
56
When a gem’s crystal structure splits light into two rays that each travel at a slightly different speed and direction, it’s called
double refraction
## Footnote
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.
57
Which phenomenon is a broad color flash?
Labradorescence
## Footnote
A broad color flash is the characteristic appearance of labradorescence.
58
Which element does chromium substitute for to cause ruby’s red?
Aluminum
## Footnote
In ruby, chromium is the trace element that substitutes for aluminum in the gem’s crystal structure to give the gem its red color.
59
Which element causes the finest reds and greens in gemstones?
Chromium
## Footnote
Chromium causes the top red colors and the best greens in gemstones, including ruby and emerald.
60
The best-known and most valuable chatoyant gem is cat’s-eye
chrysoberyl
## Footnote
The best-known and most valuable chatoyant gem is cat’s-eye chrysoberyl.
61
Which process dissolves nutrients in chemicals to form synthetic crystals?
Flux growth
## Footnote
Chemicals dissolve the nutrients needed to form synthetic crystals by the flux growth process.
62
Which synthetic process developed rapidly due to laser research in the 1960s?
Pulling
## Footnote
The pulling process was developed to meet the need for inclusion-free synthetic ruby in laser equipment.
63
A snakeskin structural pattern is typical of which synthetic gem?
Synthetic opal
## Footnote
Synthetic opal may develop a snakeskin or honeycomb structural pattern during growth.
64
Synthetic turquoise is most likely produced by which process?
Ceramic
## Footnote
Some of the fine-grained materials produced by ceramic processes include synthetic turquoise and imitation lapis lazuli.
65
The hydrothermal growth process is the only method used to produce which synthetic gem?
Quartz
## Footnote
The hydrothermal process is the only process used to produce synthetic quartz.
66
Which synthetic process uses an autoclave?
Hydrothermal growth
## Footnote
The steel container used in the hydrothermal process is called the autoclave.
67
The flux used in the flux process is a solid material that, when molten, _______.
dissolves other materials
## Footnote
When flux is molten it becomes a chemical solution that dissolves other materials.
68
Synthetic opal is grown using microscopic silica spheres that are produced by _______.
precipitation
## Footnote
The chemical process used to produce microscopic silica spheres for growing synthetic opal is called precipitation.
69
Which process involves heating finely ground powder, sometimes under pressure, to produce a fine-grained solid material?
Ceramic
## Footnote
Ceramic processes produce fine-grained solid materials.
70
The two main types of processes for synthetic gem production are melt and _______.
solution
## Footnote
The vast majority of synthetic gems on the market today are produced by either melt or solution processes.
71
Low cost and high volume characterize which process?
Flame fusion
## Footnote
The flame-fusion process produces a large volume of synthetic gems at low cost.
72
Which process uses a heating unit that passes over a rotating solid rod of chemicals until it forms a synthetic crystal?
Floating zone
## Footnote
In the floating zone process, a chemical rod rotates as a heating unit passes over it, crystallizing in 'zones'.
73
The crucibles that work best for flux growth are made of _______.
platinum
## Footnote
The chemicals used in the flux process are very corrosive, and platinum is highly resistant to corrosion.
74
Which of the following can help trained observers separate natural from synthetic gems?
Internal and external characteristics
## Footnote
Internal and external characteristics can help trained observers separate natural from synthetic gems.
75
A laboratory-created gem with essentially the same chemical composition, crystal structure, and properties as its natural counterpart is a(n) _______.
synthetic
## Footnote
If a material is laboratory created with essentially the same chemical composition, crystal structure, and properties as its natural counterpart, it is called a synthetic.
76
Creating asterism with heat treatment is most common in
synthetic corundum
## Footnote
Heating and controlled cooling create asterism in synthetic corundum
77
Quartz or topaz with a thin layer of gold deposited on the surface is known as
aqua aura
## Footnote
Quartz and topaz coated with a thin, transparent layer of gold are often marketed as “aqua aura”
78
Written information on dyeing gems dates back to about
200 BC
## Footnote
Written Egyptian recipes for dyeing gemstones date back to 200 BC
79
What agent can create a shallow layer of asterism when it’s introduced below the surface of a corundum cabochon by lattice diffusion?
Titanium oxide
## Footnote
Lattice diffusion creates a shallow layer of asterism in corundum by introducing titanium oxide below the surface
80
Jadeite is often
bleached and polymer impregnated
## Footnote
Bleaching and then impregnating jadeite with polymer is a common treatment
81
What coloring agents do treaters use during lattice diffusion to create a shallow layer of blue color in corundum?
Iron and Titanium
## Footnote
These agents are used in the process of lattice diffusion for color enhancement
82
When a filler is so extensive that it becomes a significant component of the finished product, the result is described as
a composite
## Footnote
This refers to manufactured materials where fillers are significant
83
How deep is the color layer that lattice diffusion with titanium or chromium creates in corundum?
0.01 to 0.50 mm
## Footnote
This depth is typical for lattice diffusion-treated corundum
84
Which of these is considered a gem treatment?
Dyeing, heat treatement, bleaching, etc
## Footnote
Dyeing is a recognized treatment, whereas cutting and polishing are not
85
Treaters use sugar treatment to enhance
opal
## Footnote
Sugar treatment darkens opal and enhances its play-of-color
86
Heat treating sapphire in a reducing environment can
deepen blue color in sapphire
## Footnote
This treatment is effective for enhancing the color of blue sapphires
87
For effective clarity enhancement, the material used to fill a gem’s fractures must have nearly the same
refractive index as the gem
## Footnote
A similar refractive index helps conceal fractures effectively
88
After irradiation, which gem’s color is stable under normal wearing conditions?
Golden beryl
## Footnote
The color of irradiated golden beryl remains stable compared to other irradiated gems
89
Heat can lighten amethyst’s purple by
causing changes in color centers
## Footnote
Heat destroys color centers in amethyst, affecting its color
90
Which gem is commonly heat treated?
Amber
## Footnote
Amber is subjected to heat treatment to improve its appearance
91
The market sector where better-quality gemstones are used in well-finished, moderately priced jewelry is known as the _______
middle market
92
Which continent is seen as the major source of present and future production, yielding a wealth of colored stone varieties?
Africa
93
In mining terms, the theft of a mine’s production by its workers is known as _______
high grading
94
Today, the chosen sales outlets for premium-quality colored stones are _______
international auction houses
95
About half of all the jewelry in the world is sold in _______
the United States
96
A city, region, or country with a large number of gemstone manufacturers is called a _______
cutting center
97
The Chinese industry focuses on manufacturing in mainland China for export through _______
Hong Kong
98
The vast majority of Sri Lankan deposits are in _______
alluvial gravels
99
A gem’s origin refers to _______
the geographical place where it was mined
100
By some estimates, Thailand controlled what percentage of the global ruby and sapphire trade in the 1970s and 1980s?
80 percent
101
A commitment to reserve a portion of the resources derived from any country for the economic development of that country is called _______
beneficiation
102
Materials cut free-size are usually _______
large, important stones
103
A premium price for selecting stones from a parcel is called the _______
pick price
104
A quantity of stones of similar or mixed qualities, from a single mine or from various sources, offered for sale together is called a _______
parcel
105
Which trade term describes a mixture of gem qualities that represents unsorted production from a particular mine?
Mine run
106
What tone levels apply to transparent colored stones in GIA Colored Stone Grading?
2 through 8
## Footnote
Only tone levels 2 through 8 are used for grading colored stones.
107
How do cool-colored stones with low saturation typically appear?
Grayish
## Footnote
Generally, cool-colored stones with low saturation look grayish.
108
What is the main goal of a cutter when producing a gemstone?
Produce a stone with the highest possible value
## Footnote
This is especially true when the rough is expensive and rare.
109
What causes extinction in gemstones?
Deep pavilions
## Footnote
A deep pavilion usually causes extinction, while shallow ones typically cause windows.
110
Which two coloring agents are primarily responsible for color change in gemstones?
Chromium and vanadium
## Footnote
Chromium and vanadium cause the color-change phenomenon in most gemstones.
111
What should be done to a gem before assessing its color?
Clean the stone and view it on a neutrally colored background
## Footnote
Neutral background colors have the least effect on the appearance of a gemstone’s color.
112
Which gemstone is known to occur in almost every color?
Tourmaline
## Footnote
Tourmaline comes in a wide range of colors.
113
What is the abbreviation for a slightly purplish red hue in the GIA Colored Stone Grading System?
slpR
## Footnote
In GIA Colored Stone Grading System color abbreviations, the dominant hue is always capitalized.
114
What is the first impression of an object's basic color called?
Hue
## Footnote
The first impression of an object’s basic color is its hue.
115
Variations in conditions during crystal growth can lead to what phenomenon?
Color zoning
## Footnote
Variations in conditions and coloring agents that occur during crystal growth can result in color zoning.
116
What is the standard lighting for grading colored stones?
Daylight-equivalent fluorescent
## Footnote
Daylight-equivalent fluorescent is the standard lighting for grading colored stones.
117
What happens when a singly refractive stone shows a second color face-up?
Light reflected within the stone interacts with light transmitted through it
## Footnote
Some singly refractive stones can show a second color face-up.
118
Most defects in colored stone proportions are due to what?
Compromises made by the cutter
## Footnote
Most defects in colored stone proportions—for example, windows and extinction—are compromises made by the cutter to produce economically viable gems.
119
True or False: Hues at the extremes of the tone range typically have high saturation.
False
## Footnote
Generally, hues at opposite extremes of the tone range—very light or very dark—commonly don’t reach levels of saturation as high as those in medium tones.
120
Use trade terms that imply geographic origin only if the _______ is known.
gem’s actual source
## Footnote
To avoid misunderstandings, only use a trade term implying geographic origin if the gem’s actual source is known.
121
Which type of rough is most likely to undergo cobbing?
Commercial-quality amethyst rough
## Footnote
Lower-cost gems are the most likely to undergo cobbing.
122
A carved design that projects slightly from a flat or curved surface is called a(n)
cameo
## Footnote
A cameo has a carved design that projects slightly from its surface.
123
Which cutting stage has the greatest impact on the value of the finished gem?
Preforming
## Footnote
Preforming has the greatest impact on the value of the finished gem.
124
Translucent to opaque rough is often cut into a
cabochon
## Footnote
Translucent to opaque rough is usually cut as a cab as opposed to being faceted.
125
Colored stones cut flat with shallow pavilions usually have areas of lower color intensity called
windows
## Footnote
Windows are areas of lower color intensity.
126
Excessive bulge on a step cut
adds weight
## Footnote
Excessive bulge on a step cut is there to add weight to the finished stone.
127
Cutters can darken the color of pale stones by cutting a
deep pavilion
## Footnote
A deep pavilion will darken a pale stone.
128
Rough that’s ground to the approximate shape of the finished stone is called
preform
## Footnote
Rough that is ground to the approximate shape of the finished stone is called a preform.
129
To judge brilliance, view the stone
face-up
## Footnote
Brilliance is always judged by viewing the stone face-up.
130
Which colored stone variety has cutting challenges due to vulnerable cleavage planes?
Tanzanite
## Footnote
Tanzanite has two directions of cleavage.
131
Important factors in evaluating a faceted gem’s proportions are its crown and pavilion depths and
the symmetry of its profile and its face-up outline
## Footnote
Important factors in evaluating a faceted gem’s proportions are its crown and pavilion depths, the symmetry of its profile, and its face-up outline.
132
When viewed face-up, a stone with more than 75 percent brilliance is considered to have
excellent proportions
## Footnote
If the face-up brilliance is more than 75 percent, it generally means the basic proportions of the stone are excellent.
133
Which type of rough is usually faceted?
Transparent
## Footnote
Most transparent rough is faceted.
134
To retain as much weight as possible from rare, high-quality rough, cutters would most likely vary
proportions
## Footnote
Varying proportions will save the most weight from valuable rough.
135
Removing heavily included sections from gemstone rough by carefully tapping it with a small hammer is known as
cobbing
## Footnote
Cobbing is used to remove included areas by tapping rough crystals with a small hammer.
136
In which colored stone clarity type are the gems usually eye-clean?
Type I
## Footnote
Type I stones are usually eye-clean.
137
Fingerprints are
partially healed fracture planes
## Footnote
Fingerprints are partially healed fracture planes.
138
An angular, hollow space that resembles a mineral inclusion is called a
negative crystal
## Footnote
Negative crystals are angular hollow spaces that resemble mineral inclusions.
139
The term 'silk' describes
a group of fine, needle-like inclusions
## Footnote
Silk describes a group of fine, needle-like inclusions.
140
Which of these clarity characteristics usually have the greatest impact on a gem’s marketability?
A large, unhealed feather under its table
## Footnote
A large, unhealed feather located under the table would have the greatest impact on clarity.
141
A characteristic or irregularity confined to the surface of a polished gemstone is a(n)
blemish
## Footnote
If a clarity characteristic is confined to the surface of a gem, it’s called a blemish.
142
Gems that are usually eye-clean include
spodumene, yellow beryl, and aquamarine
## Footnote
Spodumene, yellow beryl, and aquamarine are usually eye-clean.
143
The highest clarity grade for colored stones is
eye-clean
## Footnote
Eye-clean is the highest clarity grade for colored stones.
144
Growth zoning in a colored stone is evidence of
crystal growth
## Footnote
Growth zoning is evidence of a crystal’s growth process.
145
An inclusion with the most negative impact on a colored stone’s clarity would be located
under the table
## Footnote
Inclusions under the table have the most impact on a stone’s clarity.
146
Inclusions are important to gemologists because they
can help separate natural from synthetic gems
## Footnote
Inclusions can help separate natural from synthetic gems.
147
In which of the following colored stone clarity grades do the definitions vary for each clarity type?
Moderately included
## Footnote
The definitions in the moderately included grade vary for each clarity type.
148
Two factors that determine an inclusion’s impact on a gem’s value are
position and relief
## Footnote
The five factors that determine an inclusion’s impact on a gem’s value are nature, size, number, position, and relief.
149
In terms of clarity, what gem is classified as Type III?
Emerald
## Footnote
Emerald is a Type III gem.
150
A general term for a break in a stone is
feather
## Footnote
Feather is a general term for a break in a stone.
151
What is the per-carat price of an emerald that weighs 3.50 cts. and costs $10,500.00?
$3,000.00
## Footnote
Divide $10,500.00 by 3.50 cts.
152
Sieves are most useful for sorting round gems with diameters of what size?
3 mm and below
## Footnote
See 'Sieves' in Colored Stones Assignment 11.
153
What are individual stone prices referred to as?
unit prices
## Footnote
See 'Carat Weight and the Gem Business' in Colored Stones Assignment 11.
154
If a parcel of sapphires weighs 382.00 cts. and the per-carat price is $80.00, what is the total cost of the parcel?
$30,560.00
## Footnote
Multiply the parcel’s carat weight by the price per carat.
155
The color of a sorting pad should be what?
neutral
## Footnote
See 'Tools of the Trade' in Colored Stones Assignment 11.
156
When counting a large pile of small gems, it’s best to separate them into groups of how many?
5
## Footnote
See 'Counting Gems' in Colored Stones Assignment 11.
157
Colored stones with higher values usually have what characteristics?
medium to medium-dark tone and vivid saturation
## Footnote
See 'Color' in Colored Stones Assignment 11.
158
How are most colored stones sold?
by weight
## Footnote
See 'Weights and Measures' in Colored Stones Assignment 11.
159
If a parcel of amethysts contains 1,000 stones and weighs 1,542.00 cts. with a per-carat price of $0.75, what is the unit price?
$1.16
## Footnote
Multiply 1,542.00 cts. by $0.75 for the parcel price, then divide by 1,000.
160
A metric carat equals how many grams?
0.20 gram
## Footnote
See 'Carat Weight and the Gem Business' in Colored Stones Assignment 11.
161
What is the international unit of measurement for gem weight?
metric carat
## Footnote
See 'Carat Weight and the Gem Business' in Colored Stones Assignment 11.
162
How many points are in a metric carat?
100
## Footnote
See 'Carat Weight and the Gem Business' in Colored Stones Assignment 11.
163
A gem’s price divided by its carat weight is called what?
per-carat price
## Footnote
See 'Carat Weight and the Gem Business' in Colored Stones Assignment 11.
164
What category of colored stone is often sold per piece?
Small, inexpensive
## Footnote
See 'Weights and Measures' in Colored Stones Assignment 11.
165
What is the cost of a ruby that weighs 5.76 cts. and has a per-carat price of $5,500.00?
$31,680.00
## Footnote
Multiply 5.76 cts. by $5,500.00.
166
What is the most valuable tone and saturation for ruby?
Medium to medium-dark tone and vivid saturation.
## Footnote
See “Color” in Colored Stones Assignment 12.
167
Which location supplied most of the world’s commercial-quality rubies through the 1990s?
Mong Hsu, Myanmar.
## Footnote
See “Myanmar” in Colored Stones Assignment 12.
168
The flame-fusion method for creating synthetic rubies is also known as?
The Verneuil method.
## Footnote
See “Synthetics” in Colored Stones Assignment 12.
169
What is the most common crystal habit for ruby?
Tabular hexagonal prism.
## Footnote
Crystals from some sources can be elongated prisms and bipyramids. See “Size and Cut” in Colored Stones Assignment 12.
170
Which types of synthetics have inclusions and growth structures that might closely resemble natural rubies?
Flux and hydrothermal synthetics.
## Footnote
See “Synthetics” in Colored Stones Assignment 12.
171
Types of clarity enhancement in ruby include oiling and _______.
Glass filling.
## Footnote
See “Clarity Enhancement” in Colored Stones Assignment 12.
172
When can you describe a stone by a source name?
Only if you’re sure the stone came from that source.
## Footnote
See “Colors and Qualities Associated with Source Names” in Colored Stones Assignment 12.
173
Ruby deposits in Thailand and Cambodia are associated with _______.
Alkali basalt.
## Footnote
See “Causes of Ruby Color” in Colored Stones Assignment 12.
174
What happens when Mong Hsu rubies are heat treated?
Eliminates dark centers or cores.
## Footnote
Heating Mong Hsu rubies also required clarity improvements to make them marketable. See “Heating to Remove Blue Color” and “Flux Healing” in Colored Stones Assignment 12.
175
Rubies that come from marble deposits are typically low in _______.
Iron.
## Footnote
Marble’s iron content is low, so rubies originating in marble lack iron. See “Causes of Ruby Color” in Colored Stones Assignment 12.
176
What is considered ruby’s major cutting, treatment, and wholesale trading center?
Thailand.
## Footnote
Other important centers include Jaipur, India, Sri Lanka, and China’s Guangdong Province. See “The Global Ruby Market” in Colored Stones Assignment 12.
177
Ruby can command the highest per-carat price of all colored stones, especially when it’s _______.
Untreated.
## Footnote
See “Ruby” in Colored Stones Assignment 12.
178
Corundum can only form in an environment that is low in _______.
Silicon.
## Footnote
Corundum forms under the right temperature and pressure conditions. See “Causes of Ruby Color” in Colored Stones Assignment 12.
179
By the beginning of 2010, which area had emerged as the world’s most important ruby source?
Montepuez in northern Mozambique.
## Footnote
See “Mozambique” in Colored Stones Assignment 12.
180
The rubies found in the mountains of Tajikistan, Afghanistan, and Pakistan are all _______.
Marble-hosted.
## Footnote
See “Central Asia” in Colored Stones Assignment 12.
181
Regions associated with basalt-related sapphire include Cambodia, Thailand, Nigeria, and _______
Australia
## Footnote
These regions are known for their basalt-related sapphire deposits.
182
The most highly valued blue sapphire hues are _______
blue to violetish blue
## Footnote
This hue is considered the most desirable in the market.
183
Minute inclusions can give Kashmir sapphires a(n) _______ appearance.
velvety
## Footnote
This appearance is characteristic of high-quality Kashmir sapphires.
184
Which source emerged in the 1990s as a significant source of good- to fine-quality sapphire?
Madagascar
## Footnote
Madagascar has become notable for its sapphire production since the 1990s.
185
Blue sapphire’s pleochroic colors are typically _______
slightly greenish blue and slightly violetish blue
## Footnote
Pleochroism refers to the ability of a mineral to show different colors when viewed from different angles.
186
Kashmir’s most important sapphire production period was from _______ to _______
1881 to 1887
## Footnote
This period marked the peak of sapphire production in Kashmir.
187
Blue sapphire’s most common crystal habit is a(n) _______
spindle-shaped hexagonal pyramid or bipyramid
## Footnote
This crystal habit is typical for corundum gemstones.
188
Blue sapphires that originate in basaltic rock generally have _______
high iron content
## Footnote
High iron content contributes to the color characteristics of these sapphires.
189
What location supplies sapphires that are probably not heat treated?
Yogo Gulch
## Footnote
Yogo Gulch sapphires are known for their natural color without heat treatment.
190
Which country is the biggest market for sapphire?
The United States
## Footnote
The US accounts for about half of the global sapphire market.
191
Australian sapphire’s blue color is often described as _______
inky
## Footnote
This description reflects the deep, rich color of Australian sapphires.
192
What trace elements cause blue sapphire’s color?
Titanium and iron
## Footnote
These elements are crucial for the development of blue hues in sapphires.
193
Most fine sapphires over 100 cts. come from _______
Sri Lanka
## Footnote
Sri Lanka is renowned for producing large, high-quality sapphires.
194
Milky, grayish, or brownish corundum that can be treated to a fine blue color is called _______
geuda
## Footnote
Geuda sapphires can be enhanced through treatment to achieve a desirable blue color.
195
When trade members use the single word 'sapphire,' they are referring to _______
the blue variety of corundum
## Footnote
In trade contexts, 'sapphire' typically denotes blue corundum rather than other colors.
196
What causes asterism in black star sapphire?
Hematite inclusions.
## Footnote
Hematite inclusions cause asterism in black star sapphires.
197
Which color of star sapphire is usually cut shallow due to parting?
Pink.
## Footnote
To review this topic and find the correct answer, see 'Judging the Cut' in Colored Stones Assignment 14.
198
In which decade were the first flame-fusion star rubies produced?
1940s.
## Footnote
Union Carbide’s Linde division produced the first flame-fusion star rubies and sapphires in 1947.
199
How readily available is green sapphire?
Readily available.
## Footnote
Green sapphires are readily available.
200
What does the name 'padparadscha' mean?
Lotus flower.
## Footnote
Padparadscha is the Sinhalese word for lotus flower.
201
Which fancy sapphire hue regularly commands top prices?
Pink.
## Footnote
Fine pink sapphires regularly command top prices, sometimes comparable to padparadscha.
202
What causes sapphire's color change?
Vanadium.
## Footnote
Vanadium causes color change in sapphire.
203
What is the best-quality star corundum?
Semitransparent.
## Footnote
The best-quality star corundum is semi-transparent.
204
What is the most common number of rays in star corundum?
6.
## Footnote
Star corundum usually has 6 rays.
205
Color-change sapphire typically changes from blue or violet to _______.
strongly reddish purple.
## Footnote
Color-change sapphire typically changes from blue or violet to violetish purple or strongly reddish purple.
206
Fancy sapphires from Montana tend to be _______.
light in tone.
## Footnote
Fancy sapphires from Montana tend to be light in tone.
207
What is the most prized star corundum bodycolor?
Red.
## Footnote
The most prized star corundum bodycolor is red.
208
What causes the pink color of corundum?
Chromium.
## Footnote
Chromium causes the pink color of corundum.
209
What is a common trade name for intensely saturated sapphire displaying a combination of pink and orange hues without any noticeable brown coloring?
Padparadscha.
## Footnote
The trade name for intensely saturated sapphire displaying a combination of pink and orange hues without any noticeable brown coloring is padparadscha.
210
A major source of black star sapphire is _______.
Thailand.
## Footnote
Thailand is a major source of black star sapphire. Another significant source is Australia.
211
Who produced a hydrothermal synthetic emerald in the 1960s by depositing a synthetic emerald layer over faceted beryl seeds?
Johann Lechleitner
## Footnote
This process involved layering synthetic material onto beryl seeds to create emeralds.
212
Which element gives emerald a bluer green color?
Iron
## Footnote
The presence of iron increases the blue hue in emeralds.
213
What percentage of the world’s emerald supply is estimated to come from Zambia’s Kagem mine?
20 percent
## Footnote
Kagem mine is a significant source for global emerald production.
214
Most facet-grade emerald mined in Brazil is from Itabira, Nova Era, and _______.
Capoeirana
## Footnote
These areas are known for producing high-quality emeralds.
215
Government geological surveys of Colombia’s emerald reserves suggest that _______.
only 20 percent of the country’s emeralds have been mined
## Footnote
This indicates significant potential for future mining.
216
Which country is the number one supplier to the US in terms of total carats?
India
## Footnote
India plays a crucial role in supplying emeralds to the US market.
217
To emphasize the bluish green color, cutters orient a fashioned emerald with its table _______.
perpendicular to the crystal length
## Footnote
This orientation enhances the color quality of the emerald.
218
The safest way to clean emeralds is with _______.
gentle scrubbing with warm, soapy water
## Footnote
Ultrasonic or steam cleaning is not recommended due to common filled fractures.
219
What’s the estimated percentage of emeralds with fractures filled with oil or resin?
90 percent or more
## Footnote
This is a common treatment to enhance the appearance of emeralds.
220
In Colombia, modern mechanized mining of emerald by private companies began in _______.
1977
## Footnote
This marked a significant change in the mining landscape in Colombia.
221
The great majority of emeralds come from Colombia, Zambia, Brazil, and _______.
Afghanistan and Pakistan
## Footnote
These regions are key sources of emerald production.
222
The trade term 'Zambian' describes emeralds that are _______.
slightly darker and more bluish than 'Colombian'
## Footnote
This distinction helps in categorizing emeralds based on their origin.
223
The most desirable emerald hues are _______.
bluish green to green
## Footnote
These colors are preferred due to their vibrancy and saturation.
224
Brazilian emeralds are mined from _______.
areas where pegmatites intersect with schists
## Footnote
This geological setting is crucial for emerald formation.
225
Colombia and Brazil cut most of their better-quality emerald rough and send the lower-quality material to _______.
Jaipur, India
## Footnote
Jaipur is known for processing lower-quality gemstones.
226
Chinese freshwater cultured pearls first appeared on the international market around _____
1970
## Footnote
Chinese freshwater cultured pearls gained international recognition in the early 1970s.
227
By what date had Kokichi Mikimoto begun culturing whole pearls?
1908
## Footnote
Kokichi Mikimoto was a pioneer in pearl culturing and expanded his market internationally by 1920.
228
Aragonite is a crystallized form of _____
calcium carbonate
## Footnote
Aragonite is a key component in the formation of nacre, which is essential for pearl development.
229
A number of similar cultured pearl strands bundled together is called a _____
hank
## Footnote
Hanks are often used in the pearl market for selling strands of pearls.
230
South Sea cultured pearls are produced principally in Australia, Indonesia, Myanmar, and _____
the Philippines
## Footnote
These regions are known for their large and high-quality South Sea pearls.
231
The oyster used to grow Tahitian cultured pearls is the _____
Pinctada margaritifera
## Footnote
This species is known for producing dark-colored pearls, which are highly valued.
232
Which industry directly contributed to the decline of the natural pearl industry?
Oil
## Footnote
The oil industry in the Persian Gulf affected the natural pearl industry through pollution and economic shifts.
233
Seed pearls are _____
very small natural pearls
## Footnote
The term 'seed pearl' is specifically used for small pearls that occur naturally.
234
The nacreous layer inside a pearl-bearing mollusk’s shell is called _____
mother-of-pearl
## Footnote
Mother-of-pearl is also known as nacre and is crucial for pearl formation.
235
Saltwater cultured whole pearls grow from a _____
mantle-tissue piece and a bead nucleus
## Footnote
This method involves implanting a bead and tissue to stimulate pearl growth in mollusks.
236
Between 1992 and 2006, oysters in many important Japanese cultured pearl farming areas began to _____
die off in massive numbers
## Footnote
This decline significantly impacted the production of cultured pearls in Japan.
237
The organ that lines the mollusk’s shell, encloses its soft body, and contains the cells that form pearl sacs and secrete nacre is the _____
mantle
## Footnote
The mantle plays a crucial role in the formation of pearls by secreting nacre.
238
The first South Sea cultured pearl farm was founded in which country?
Australia
## Footnote
This farm was established in the 1950s and marked the beginning of the South Sea pearl industry.
239
Pearl is _____
an organic gem
## Footnote
Pearls are unique among gemstones as they are produced by living organisms.
240
The four major types of cultured whole pearls are akoya, South Sea, freshwater, and _____
Tahitian
## Footnote
These four types represent the most commercially significant cultured pearls in the market.
241
Usually, the diameters of the cultured pearls in a strand vary from each other by no more than _______
0.5 mm
## Footnote
Buyers expect the cultured pearls in a strand to be within 0.5 mm of each other.
242
To bleach akoya pearls, processors use _______
a combination of hydrogen peroxide and fluorescent light
## Footnote
Akoya processors use a combination of hydrogen peroxide and bright fluorescent light to bleach their pearls.
243
Pearl colors tend to be _______
low in saturation
## Footnote
While pearls occur in a broad range of hues and a wide range of tones, they usually have low saturation.
244
Pearls that show noticeable blemishes are classified as _______
Moderately Spotted
## Footnote
The GIA Pearl Description System classifies pearls that show noticeable blemishes as Moderately Spotted.
245
What happens when saltwater cultured pearls are exposed to gamma rays?
Bead nucleus darkens
## Footnote
When saltwater cultured pearls are exposed to gamma rays, the freshwater mussel shell-bead nuclei darken.
246
A procedure that includes cleaning, buffing, and sometimes bleaching, done to make cultured pearls presentable and appealing, is called _______
a process
## Footnote
A procedure that includes cleaning, buffing, and sometimes bleaching, done to make cultured pearls presentable and appealing, is called a process.
247
The best way to clean pearls is with _______
warm, mild soapy water
## Footnote
Warm, mild soapy water is the best and safest way to clean pearls.
248
The matching level that describes a group of pearls with minor variations in uniformity is _______
Good
## Footnote
The GIA Pearl Description System classifies a group of pearls having minor variations in uniformity as Good.
249
The nacre quality classification described as 'Nucleus not noticeable, no chalky appearance' is _______
Acceptable
## Footnote
The GIA Pearl Description System classifies as Acceptable cultured pearls with a nucleus that is not noticeable and no chalky appearance.
250
The trade term for Tahitian cultured pearls with a dark green-gray to blue-gray bodycolor and rosé to purple overtones is _______
peacock
## Footnote
Peacock is the successful marketing trade term for Tahitian cultured pearls with a dark green-gray to blue-gray bodycolor and rosé to purple overtones.
251
Essence d’orient is a mixture of _______
fish scales and varnish
## Footnote
A mixture of iridescent fish scales and varnish makes up essence d’orient, which is used to coat glass beads and create realistic-looking pearl imitations.
252
Which overtone color increases the value of akoya cultured pearls with white bodycolor?
Rosé
## Footnote
A rosé overtone on an akoya cultured pearl with white bodycolor increases its value.
253
In pearl culturing, the most difficult shape to produce is _______
round
## Footnote
Round is the most difficult shape to culture and, all other value factors being equal, rounds are the most valuable.
254
At most pearl farms, post-harvest procedures consist of washing and _______
polishing in a solution of water and salt
## Footnote
At most pearl farms, post-harvest procedures consist of simply washing and polishing the cultured pearls.
255
When mollusks live in cooler water, they form _______
pearls with higher luster
## Footnote
Mollusks living in cooler water deposit nacre more slowly than those in warmer water, causing their nacre to be more translucent and have a higher luster.
256
What is Polar jade actually classified as?
nephrite
## Footnote
Polar jade is a trade term for fine green nephrite.
257
What is the trade name for the finest-quality jadeite?
Imperial
## Footnote
Imperial is the trade name for the finest-quality, semitransparent jadeite with even, vivid green coloration.
258
What is rough nephrite recovered from alluvial deposits called?
river jade
## Footnote
River jade often occurs as smooth, fairly transparent pebbles.
259
What color might heat treatment of jadeite produce?
brownish orange
## Footnote
Heat treatment can produce a brownish orange color in iron-bearing jadeite.
260
What is Type C jadeite?
dyed
## Footnote
Dyed jadeite is known as Type C jadeite.
261
What is mutton-fat jade a trade name for?
top-quality white nephrite
## Footnote
Mutton-fat jade is a trade name for top-quality white nephrite.
262
What are today’s most common jade imitations?
glass and plastic
## Footnote
Glass and plastic are today’s most common jade imitations.
263
What causes jadeite’s finest green color?
chromium
## Footnote
The finest green color of jadeite is caused by chromium.
264
What is the center of the jadeite mining district in Myanmar?
Hpakant
## Footnote
The small town of Hpakant is the center of the jadeite mining district in Myanmar.
265
Where was jadeite first used as an ornamental object?
Central America
## Footnote
Jadeite was first fashioned and used as an ornamental object in Central America as early as 1500 BC.
266
What is Type B jadeite?
bleached and impregnated
## Footnote
Bleached and impregnated jadeite is known as Type B jadeite.
267
What are spots of color near the surface of a jadeite boulder called?
show points
## Footnote
Show points are spots of color near the surface of a jadeite boulder that can be seen through thin skin.
268
What is the most valuable level of transparency in jadeite?
semitransparent
## Footnote
Semitransparent is the most valuable transparency level of jadeite.
269
What is the finest texture category of jadeite known as?
old mine
## Footnote
Old mine is the finest texture category of jadeite.
270
How is the toughness of jadeite described?
exceptional
## Footnote
Jadeite has exceptional toughness.
271
Where was plastic imitation opal first marketed?
Japan
## Footnote
Plastic imitation opal was first marketed in the late 1980s.
272
What is the term for a pattern of large, distinct, usually rectangular patches of play-of-color in opal?
harlequin
## Footnote
A harlequin pattern shows edges that touch each other.
273
What is the background color of semi-black opal?
Grayish
## Footnote
Semi-black opal has a specific grayish background color.
274
What is the transparency of gray-base black opal?
Opaque
## Footnote
Gray-base black opal is characterized by its opaque transparency.
275
Boulder opal consists of thin layers of precious opal cut to include a matrix of sandstone or _______.
ironstone
## Footnote
Ironstone often serves as a reinforcing layer behind the gem.
276
What causes fire opal’s background color?
iron impurities
## Footnote
Experts believe that iron impurities are responsible for this color.
277
Who created the first marketable synthetic opal?
Pierre Gilson
## Footnote
Pierre Gilson is credited with this innovation.
278
What is the main source of fine-quality black opal in the world?
New South Wales
## Footnote
This region remains the primary source for black opals.
279
Which treatment involves immersing opal in concentrated sulfuric acid?
Sugar
## Footnote
This treatment involves heating opals in a sugar-saturated solution.
280
What is the transparency range of white opal’s background?
Translucent to opaque
## Footnote
White opal can range in transparency from translucent to opaque.
281
Opal is composed primarily of _______.
hydrous silica
## Footnote
This is the basic chemistry of opal.
282
Opal types are often based on _______.
background color
## Footnote
The classification of opals frequently depends on their background color.
283
What is the play-of-color seen only when light travels through an opal to the eye called?
contra luz
## Footnote
Contra luz opals exhibit play-of-color when light is transmitted through them.
284
Most opal formed between _______ million years ago.
7,000 to 110
## Footnote
This time frame is believed to be the origin of opal.
285
What is the first step in evaluating an opal?
Determine its type
## Footnote
Knowing the type is crucial as each has its own value factors.
286
In the nineteenth century, a major source of amethyst was discovered in _______
Brazil
287
The only source of natural ametrine is _______
Bolivia
288
The color of amethyst results from _______ acting on iron.
color centers
289
Which of the following has the smallest crystal size? _______
Cryptocrystalline aggregates
290
The finest amethyst colors are _______.
medium-dark to dark reddish purple or purple
291
Cryptocrystalline quartz aggregate is known as _______.
chalcedony
292
“Marabá” amethyst is often _______.
uniform in color
293
Both tiger’s-eye and hawk’s-eye quartz are _______.
microcrystalline aggregates
294
Chalcedony with curved or angular bands or layers that differ in color and transparency is known as _______.
agate
295
The trade term “black onyx” is used for _______.
treated black chalcedony
296
Most of the citrine in the market is _______.
produced by heating amethyst
297
The color of chrysoprase is _______.
yellowish green
298
Dark amethyst is lightened by _______.
heating
299
The major producer of green aventurine quartz is _______.
India
300
The world’s major commercial-quality amethyst source is _______.
Brazil
301
Most of the citrine in the market is produced by _______.
heating amethyst
## Footnote
Heating amethyst produces most of the citrine available in the market.
302
In the nineteenth century, a major source of amethyst was discovered in _______.
Brazil
## Footnote
A large amethyst deposit was discovered in Brazil in the nineteenth century.
303
Which of the following has the smallest crystal size?
Cryptocrystalline aggregates
## Footnote
Cryptocrystalline aggregates have the smallest crystal size.
304
The color of chrysoprase is _______.
yellowish green
## Footnote
Chrysoprase is yellowish green.
305
The finest amethyst colors are _______.
medium-dark to dark reddish purple or purple
## Footnote
The finest amethysts are a strongly saturated medium-dark to dark reddish purple or purple, with no visible color zoning.
306
Both tiger’s-eye and hawk’s-eye quartz are _______.
microcrystalline aggregates
## Footnote
Tiger’s-eye and hawk’s-eye quartz are microcrystalline aggregates. Their chatoyancy is caused by fibrous structures.
307
The world’s major commercial-quality amethyst source is _______.
Brazil
## Footnote
Brazil is the world’s major commercial-quality amethyst source.
308
Cryptocrystalline quartz aggregate is known as _______.
chalcedony
## Footnote
Chalcedony is a cryptocrystalline quartz aggregate.
309
Chalcedony with curved or angular bands or layers that differ in color and transparency is known as _______.
agate
## Footnote
Agate is the chalcedony variety with curved or angular bands or layers that differ in color and transparency.
310
The color of amethyst results from _______.
color centers acting on iron
## Footnote
The color of amethyst comes from color centers caused by natural irradiation acting on trace elements of iron in its crystal structure.
311
The only source of natural ametrine is _______.
Bolivia
## Footnote
The Anahi mine in eastern Bolivia is the only source of natural ametrine.
312
Dark amethyst is lightened by _______.
heating
## Footnote
Heating dark amethyst can lighten it.
313
The trade term 'black onyx' is used for _______.
treated black chalcedony
## Footnote
Chalcedony that has been treated to a solid black color is called 'black onyx' in the trade.
314
The major producer of green aventurine quartz is _______.
India
## Footnote
The major producer of green aventurine quartz is India. Other sources include Brazil, Russia, and Tanzania.
315
'Marabá' amethyst is often _______.
uniform in color
## Footnote
Marabá amethyst is often less saturated in color than amethyst from other Brazilian sources, but its color is more uniform.
316
When was alexandrite discovered?
1830
## Footnote
Discovered by miners in the Ural Mountains of Russia.
317
What is the most prized color of tanzanite?
Pure blue or intense violet-blue
## Footnote
Similar to fine sapphire.
318
Where was tanzanite discovered?
Merelani
## Footnote
Discovered in the Merelani area of Tanzania in 1967.
319
What changes during alexandrite’s color-change effect?
Hue
## Footnote
Tone and saturation usually remain the same.
320
What causes the color change in alexandrite?
Chromium
## Footnote
Responsible for the color change in alexandrite.
321
What is the most prized chatoyant gem?
Cat’s-eye chrysoberyl
## Footnote
Considered the most prized chatoyant gem in the world.
322
Almost all tanzanite is _______.
heat treated
## Footnote
About 95 percent of blue tanzanites owe their color to heat treatment.
323
Is iolite treated?
Untreated
## Footnote
This is a selling point compared to other blue gems.
324
Which pleochroic gem is the most economically important of
Iolite, Tanzanite, Andalusite, and Chiastolite?
Tanzanite
## Footnote
More economically important than iolite, andalusite, or chiastolite.
325
What is the typical color of untreated tanzanite?
Brownish
## Footnote
Untreated tanzanite typically exhibits a brownish color.
326
Who named tanzanite?
Tiffany & Co.
## Footnote
They named the transparent blue variety of zoisite tanzanite.
327
What is the most valuable main face-up color of iolite?
Blue
## Footnote
Iolite can show different bodycolors due to pleochroism.
328
Tanavyte is a trade name for _______.
purple synthetic YAG
## Footnote
Sometimes used as a tanzanite imitation.
329
What color is top-quality alexandrite in daylight?
Bluish green
## Footnote
This is the most prized color range for alexandrite in daylight.
330
Which country is a major source of cat’s-eye chrysoberyl?
Sri Lanka
## Footnote
Recognized as a significant source for this gem.
331
What must yellow to reddish brown topaz contain to attain a treated pink color?
chromium
## Footnote
Yellow to reddish brown topaz must contain chromium to attain a pink color when heat treated.
332
What is the most important source of aquamarine?
Brazil
## Footnote
Brazil is the most important source of aquamarine.
333
Where is the world’s major source of imperial and red topaz?
Ouro Preto
## Footnote
Ouro Preto, Brazil, is the world’s major commercial source of imperial and red topaz.
334
In which US state is the only source of red beryl located?
Utah
## Footnote
Utah is the world’s only source of gem-quality red beryl.
335
Which is the rarest beryl?
Red beryl
## Footnote
Red is the rarest beryl.
336
What causes natural pink, red, and violet-to-purple colors in topaz?
chromium
## Footnote
Chromium causes natural pink, red, and violet-to-purple colors in topaz.
337
What is the color range of imperial topaz?
reddish orange to orange-red
## Footnote
Imperial topaz is a widely used trade term for gem-quality topaz of medium reddish orange to orange-red color.
338
What is the finest color range for aquamarine?
medium-dark blue to slightly greenish blue
## Footnote
Moderately strong, medium-dark blue to slightly greenish blue is the finest color range for aquamarine.
339
What is the common color of natural untreated topaz?
colorless
## Footnote
Natural untreated topaz is commonly colorless.
340
Which method is used to produce synthetic aquamarine?
Hydrothermal
## Footnote
Synthetic aquamarine is grown with the hydrothermal method, though it’s not widely available.
341
Which source emerged as a leading producer of small, commercial-quality aquamarine in the 1990s?
China
## Footnote
China is a recent source and leading producer of small, commercial-quality aquamarine.
342
What are the most valuable topaz varieties?
pink and red
## Footnote
Pink and red varieties of topaz are usually the most rare and valuable.
343
What color is morganite beryl?
Pink
## Footnote
Morganite beryl is pink.
344
How is most aquamarine's color improved?
heat
## Footnote
Virtually all aquamarine has its color improved by heat.
345
What does the term 'precious topaz' refer to?
orange-to-yellow stones
## Footnote
Orange-to-yellow and brown topaz are referred to as precious topaz.
346
What is the cause of color in peridot?
Iron
## Footnote
Iron is the cause of peridot’s color.
347
Which countries produce the finest peridot?
Myanmar and Pakistan
## Footnote
Myanmar and Pakistan produce the finest-quality peridot.
348
The color of blue zircon is usually due to _______.
heat treatment
## Footnote
Almost all blue zircons on the market owe their color to heat treatment.
349
Most gem tourmalines are _______.
elbaite
## Footnote
Most tourmalines used as gemstones are elbaites, which are rich in sodium, lithium, aluminum, and sometimes copper.
350
Paraíba tourmaline is colored by _______.
copper
## Footnote
Traces of copper cause the colors of Paraíba tourmaline.
351
For the most part, rubellite tourmaline is colored by _______.
manganese
## Footnote
Manganese is the trace element that causes the color of most rubellite.
352
Many green and blue tourmalines are lightened by _______.
heating
## Footnote
Heat treatment is used to lighten the color of many dark green and blue tourmalines.
353
Metamict zircons are described as _______.
low zircons
## Footnote
Metamict zircons are often described as low zircons due to their lower properties.
354
The most expensive variety of tourmaline is _______.
Paraíba
## Footnote
The intense colors of Paraíba tourmaline make it the most expensive tourmaline variety.
355
Which trade term is used for blue tourmaline?
Indicolite
## Footnote
The trade term 'indicolite' is used for tourmaline that has a dominant blue hue.
356
What is peridot’s rating on the Mohs scale?
6.5 to 7
## Footnote
Peridot is one of the softer gems, at 6.5 to 7 on the Mohs scale.
357
The world’s largest producer of gem-quality tourmaline is _______.
Brazil
## Footnote
Brazil is the world’s largest producer of gem-quality tourmaline.
358
Most fine chrome tourmaline comes from Kenya and _______.
Tanzania
## Footnote
Most material comes from Tanzania and Kenya in Africa.
359
Most gem tourmalines form in _______.
pegmatites
## Footnote
Most tourmalines used as gemstones form in pegmatites.
360
Which characteristic easily distinguishes colorless zircon from diamond and synthetic cubic zirconia?
Strong doubling
## Footnote
Colorless zircon’s strong double refraction easily distinguishes it from diamond and synthetic cubic zirconia.
361
The substitution of one chemical element for another in the crystal structure of a mineral is called _______
isomorphous replacement
## Footnote
This term is used in the context of mineralogy.
362
Tsavorite and hessonite are both varieties of _______
grossular
## Footnote
Grossular is a type of garnet.
363
In general, the most desirable spinel color is _______
red
## Footnote
Red spinel is considered the most valuable.
364
Mandarin garnet has been used as a trade name for _______
spessartine
## Footnote
This variety is known for its vibrant orange color.
365
The most desirable, vibrant, and rare blue natural spinels are colored by _______
cobalt and iron
## Footnote
These elements contribute to the finest quality of blue spinels.
366
Rhodolite is a mixture of _______
pyrope and almandine
## Footnote
Rhodolite is a specific type of garnet.
367
The trade term malaya is used for a pinkish orange garnet that’s a mixture of _______
pyrope, spessartine, and almandine
## Footnote
Malaya garnets are known for their unique color.
368
The intense red color of spinel is caused by _______
chromium
## Footnote
Chromium is responsible for the intense colors in spinel.
369
The most important source of rhodolite in recent years has been _______
East Africa
## Footnote
East Africa is recognized for its rhodolite production.
370
The most common crystal habit of all garnets is the _______
dodecahedron
## Footnote
This is a characteristic crystal form of garnets.
371
Demantoid was first discovered in _______
Russia
## Footnote
The discovery occurred during the 1800s.
372
Tsavorite is colored by _______
vanadium
## Footnote
Vanadium gives tsavorite its distinctive green color.
373
Horsetail inclusions are found in _______
demantoid
## Footnote
These inclusions are a unique feature of demantoid garnets.
374
All garnets have essentially the same _______
crystal structure
## Footnote
Garnets belong to the cubic crystal system.
375
Spessartine is most commonly found in _______
pegmatite veins
## Footnote
Unlike many garnets, spessartine is typically found in these geological formations.
376
The trade term for top-color turquoise is
Persian.
377
The world’s largest producer of turquoise today is
the southwestern United States.
378
The finest color of turquoise is
intense medium blue.
379
The lapis lazuli trade grade that’s often spotted with green and shows obvious calcite is
Chilean.
380
Malachite’s color is caused by
copper.
381
The major source for top-color turquoise today is
China.
382
A treatment that makes turquoise less porous without the use of polymers and improves its ability to take a good polish is
the Zachery method.
383
Reconstructed turquoise is
imitation turquoise.
384
What type of mineral does turquoise usually form in?
Limonite.
385
Stabilized turquoise is a trade term for
polymer-impregnated turquoise.
386
The world’s major source of lapis lazuli is
Afghanistan.
387
What is the color of the markings that sandstone matrix creates in turquoise?
Tan.
388
The only source of charoite is
Russia.
389
The finest trade grade of lapis lazuli is
Afghan.
390
The purest blue colors of turquoise are caused by
copper.
391
Which amber color is most valuable?
Red
## Footnote
See “Amber” in Colored Stones Assignment 27.
392
Coral’s most valuable color is
Red
## Footnote
The most valuable color of coral is an intense red that dealers call oxblood.
393
Tortoise shell is composed of
Protein
## Footnote
Tortoise shell is composed of protein similar in makeup to horns, claws, and fingernails.
394
Paua is a Maori name for
Abalone
## Footnote
Paua is the Maori name for abalone shell.
395
What is one variety of conchiolin coral?
Black or Golden
## Footnote
The trade uses two conchiolin corals in jewelry: black coral and golden coral.
396
Amber is actually
tree resin that has hardened over time.
## Footnote
To be called amber, the material must be at least a million years old.
397
Immature amber is known as
Copal
## Footnote
Copal is immature amber. It is not hard enough or old enough to be considered amber.
398
What gem is a type of natural glass?
Moldavite or Obsidian
## Footnote
See “Moldavite” in Colored Stones Assignment 27.
399
Jet is an ornamental form of
lignite coal
## Footnote
Jet is an ornamental form of lignite coal that formed when wooden logs washed out to sea and sank into mud on the sea floor.
400
Which organic gem shows a structure called 'engine turning'?
Ivory
## Footnote
Ivory shows a pattern referred to as 'engine turning'.
401
The major source of jet is
England
## Footnote
Today, England is the major jet source. Whitby in Yorkshire is especially associated with the carving and finishing of jet.
402
The only source of gem-quality benitoite is
San Benito County, California
## Footnote
San Benito County, California, is the only source of gem-quality benitoite.
403
Which gem is a calcium carbonate?
Calcareous corals
## Footnote
Calcareous coral is principally calcium carbonate. Pink coral is a calcareous coral.
404
In Hawaii, black coral is
The state of Hawaii protects black coral as an endangered species.
## Footnote
See “Coral” in Colored Stones Assignment 27.
405
Which animal’s tusk produces the most valuable ivory?
Elephant
## Footnote
Elephant tusks produce the most valuable ivory, but virtually all trade in elephant ivory is illegal.
