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GIA GEM GRADING > Definitions > Flashcards

Definitions Flashcards

1
Q

SOURCE

A

A gem-producing country or area, or a particular mine in that area.

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2
Q

INORGANIC

A

Composed of, or arising from, non-living matter.

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3
Q

ORGANIC

A

Produced by, or derived from, a living organism.

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4
Q

NATURAL GEMS

A

Gems produced by natural processes, without human help.

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5
Q

ATOMS

A

The basic structural unit of all matter.

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6
Q

CHEMICAL COMPOSITION

A

Kinds and relative quantities of atoms that make up a material.

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7
Q

CHEMICAL ELEMENT

A

A substance that consists of atoms of only one kind.

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8
Q

FACETS

A

A flat, polished surface on a finished gem.

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9
Q

MINERALS

A

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

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10
Q

ROCKS

A

A natural material composed of masses of mineral crystals of one or more kinds.

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11
Q

SILICATES

A

A mineral that contains the elements silicon and oxygen.

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12
Q

CRYSTAL STRUCTURE

A

Regular, repeating internal arrangement of atoms in a material.

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13
Q

AMORPHOUS

A

Lacking a regular crystal structure.

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14
Q

GEM SPECIES

A

A broad gem category based on chemical composition and crystal structure.

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15
Q

VARIETY

A

A subcategory of species, based on color, transparency, or phenomenon.

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16
Q

PHENOMENON

A

An unusual optical effect displayed by a gem.

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17
Q

GROUP

A

A family of gems from several closely related mineral species.

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18
Q

DISCLOSURE

A

Clearly and accurately informing customers about the nature of the goods they buy.

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19
Q

CRUST

A

The surface and outermost layer of the earth.

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20
Q

MANTLE

A

A layer between the earth’s crust and its core.

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21
Q

CORE

A

The earth’s innermost layer.

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22
Q

MAGMA

A

General term for any molten rock.

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23
Q

PLATES

A

A section of the earth’s rigid outer crust.

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24
Q

PLATE TECTONICS

A

Study of the formation, structure, and movement of the plates of the earth’s crust.

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25
Q

MANTLE CONVECTION

A

Circulation in the mantle that drives the movement of the earth’s plates.

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26
Q

SUBDUCTION

A

A process that occurs when two of the earth’s plates collide, forcing one under the other.

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27
Q

OROGENIC BELTS

A

A long, widespread area in the earth’s crust where tectonic events cause major structural changes, often forming mountain ranges.

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28
Q

ROCK CYCLE

A

A constant formation and recycling process that creates new rock from old.

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29
Q

EROSION

A

The wearing away and transport of rock materials by natural forces.

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30
Q

IGNEOUS ROCKS

A

Rock formed by the crystallization of molten material.

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31
Q

METAMORPHIC ROCKS

A

A category of rocks that have been altered by heat and pressure.

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32
Q

SEDIMENTARY ROCKS

A

Rock produced from the eroded and weathered remains of existing rocks.

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33
Q

VOLCANIC

A

Pertaining to igneous activity at the earth’s surface, where magma erupts through a volcano or fissure.

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34
Q

PNEUMATOLYSIS

A

Crystallization of minerals from a gas.

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35
Q

XENOCRYST

A

A “foreign crystal” that forms in unrelated rocks and is brought to the surface as a passenger in magma.

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36
Q

PEGMATITES

A

An igneous rock typically formed from cooling, once-molten granite that follows fractures in its surrounding rock.

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37
Q

VEIN

A

A mineral deposit that occupies an existing fissure or fracture in the rock.

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38
Q

INTRUSION

A

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

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39
Q

HYDROTHERMAL FLUID

A

Hot, high-pressure solution that can dissolve, transport, and deposit minerals from one place to another.

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40
Q

REGIONAL METAMORPHISM

A

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

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41
Q

CONTACT METAMORPHISM

A

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

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42
Q

METASOMATISM

A

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.

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43
Q

GEODES

A

A spherical, often hollow, mineral-lined cavity in rock.

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44
Q

ARTISANAL MINERS

A

An independent gem or mineral prospector who typically uses small-scale, nonmechanized recovery methods.

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45
Q

OVERBURDEN

A

The material covering a gem deposit that must be removed before production can begin.

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46
Q

PRIMARY DEPOSIT

A

Gems found in the rocks that they formed in.

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47
Q

SECONDARY DEPOSITS

A

Gems found away from their primary source.

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48
Q

HEAVY MINERALS

A

Minerals dense enough to become concentrated and separated from lighter ones by the action of surface water.

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49
Q

ELUVIAL DEPOSITS

A

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

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50
Q

ALLUVIAL DEPOSITS

A

A deposit where gems are eroded from their source rock and then transported away from the source and further concentrated.

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51
Q

PLACERS

A

Workable alluvial deposit of gem minerals with economic potential.

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52
Q

UNIT CELL

A

The smallest group of atoms with both the characteristic chemical composition and crystal structure of a mineral.

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53
Q

AGGREGATES

A

A mass of tiny, randomly oriented crystals.

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54
Q

MICROCRYSTALLINE

A

An aggregate made up of individual crystals visible under magnification.

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55
Q

CRYPTOCRYSTALLINE

A

An aggregate made up of individual crystals detectable only under very high magnification.

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56
Q

TWINNING

A

Change in a gem’s crystal direction during or after growth.

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57
Q

TWINNING PLANE

A

Location of a change in crystal growth direction.

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58
Q

INCLUSIONS

A

A characteristic enclosed within a gemstone or reaching its surface from the interior.

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59
Q

LIQUID INCLUSIONS

A

Small pocket in a gem that’s filled with fluids and, sometimes, gas bubbles and tiny crystals.

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60
Q

TWO-PHASE

A

A hollow cavity in a gem, usually filled with a liquid and a gas.

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61
Q

THREE-PHASE

A

A hollow cavity in a gem filled with a liquid, a gas, and one or more crystals.

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62
Q

TRACE ELEMENTS

A

Atoms in a gem that aren’t part of its essential chemical composition.

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63
Q

HABIT

A

The characteristic external crystal shape or form of a mineral.

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64
Q

DENSITY

A

How heavy an object is in relation to its size.

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65
Q

SPECIFIC GRAVITY

A

Ratio of the weight of a material to the weight of an equal volume of water.

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66
Q

DURABILITY

A

A gemstone’s ability to withstand wear, heat, and chemicals.

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67
Q

HARDNESS

A

How well a gemstone resists scratches and abrasion.

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68
Q

TOUGHNESS

A

How well a gemstone resists breaking and chipping.

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69
Q

CLEAVAGE

A

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

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70
Q

PARTING

A

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

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71
Q

FRACTURE

A

Any break in a gem other than cleavage or parting.

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72
Q

CONCHOIDAL FRACTURE

A

A curved and ridged fracture in a gemstone, extending from the surface inward.

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73
Q

STABILITY

A

How well a gemstone resists light, heat, and chemicals.

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74
Q

THERMAL SHOCK

A

Damage caused by sudden, extreme temperature changes.

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75
Q

WAVELENGTH

A

The distance between two adjacent high points of an energy wave.

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76
Q

SELECTIVE ABSORPTION

A

Process by which a material absorbs some components of visible light and transmits others.

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77
Q

ABSORPTION SPECTRUM

A

A pattern of dark vertical lines or bands shown by certain gems when viewed through a spectroscope.

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78
Q

TRANSITION ELEMENTS

A

Elements that can selectively absorb some wavelengths of visible light and produce color in gems.

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79
Q

ALLOCHROMATIC

A

A gem colored by trace elements in its crystal structure.

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80
Q

IDIOCHROMATIC

A

A gem colored by an element that is an essential part of its chemical composition.

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81
Q

CHARGE TRANSFER

A

The movement of electrons back and forth between ions, causing the selective absorption of light.

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82
Q

INTERVALENCE CHARGE TRANSFER.

A

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

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83
Q

COLOR CENTER

A

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

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84
Q

IRRADIATION

A

Exposing a gem to manmade radiation to change or improve its color.

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85
Q

FLUORESCENCE

A

Emission of visible light by a material when it’s stimulated by ultraviolet or X-ray radiation.

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86
Q

PHOSPHORESCENCE

A

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

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87
Q

REFRACTION

A

Change in speed and possible change in direction of light as it travels from one material to another.

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88
Q

DOUBLING

A

The appearance of double images of a gemstone’s facet junctions on the side opposite the viewer.

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89
Q

DOUBLE REFRACTION

A

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

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90
Q

SINGLE REFRACTION

A

When a gem’s crystal structure doesn’t change incoming light other than by refraction and absorption.

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91
Q

OPTIC AXIS

A

Direction of single refraction in a doubly refractive gem.

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92
Q

PLEOCHROISM

A

When a gem shows different bodycolors from different crystal directions.

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93
Q

DISPERSION

A

The separation of white light into spectral colors.

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94
Q

INTERFERENCE

A

Interaction between two light rays with the same wavelengths as they travel along the same path.

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95
Q

IRIDESCENCE

A

A rainbow effect created when light is broken up into spectral hues by thin layers.

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96
Q

ORIENT

A

Iridescence seen in some natural and cultured pearls and mother-of-pearl.

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97
Q

DIFFRACTION

A

A special kind of interference phenomenon that produces patches of pure spectral colors.

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98
Q

PLAY-OF-COLOR

A

The flashing rainbow colors in opal, produced by the interaction of visible light with the gem’s microscopic internal structure of stacked silica spheres.

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99
Q

LABRADORESCENCE

A

A broad flash of color in labradorite feldspar that disappears when the gem is moved.

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100
Q

ADULARESCENCE

A

The cloudy bluish white light in a moonstone, caused by scattering of light.

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101
Q

CHATOYANCY

A

Bands of light in certain gems, caused by reflection of light from many parallel, needle-like inclusions or hollow tubes.

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102
Q

MILK AND HONEY

A

A two-toned effect seen when a chatoyant gem is positioned at right angles to a light source.

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103
Q

ASTERISM

A

Crossing of chatoyant bands, creating a star in the dome of a cabochon.

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104
Q

AVENTURESCENCE

A

A glittery effect caused by light reflecting from small, flat inclusions within a gemstone.

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105
Q

COLOR CHANGE

A

A distinct change in gem color under different types of lighting.

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106
Q

SYNTHETIC GEMS

A

A laboratory creation with essentially the same chemical composition, crystal structure, and properties as its natural counterpart.

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107
Q

IMITATION GEMS

A

Any material that looks like a natural gem and is used in its place.

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108
Q

MELT

A

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

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109
Q

SOLUTION

A

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

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110
Q

FLAME FUSION

A

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

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111
Q

PULLING

A

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

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112
Q

BOULE

A

A cylindrical synthetic crystal produced by a melt process.

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113
Q

SEED CRYSTAL

A

A tiny crystal used as a template to control the size, speed, or direction of growth and the shape of a growing synthetic crystal.

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114
Q

FLOATING ZONE

A

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

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115
Q

SKULL MELT

A

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

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116
Q

FLUX GROWTH

A

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

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117
Q

HYDROTHERMAL GROWTH

A

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

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118
Q

SPONTANEOUS NUCLEATION

A

A synthetic-crystal growth method that starts without a seed crystal.

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119
Q

CERAMIC PROCESSES

A

A process in which finely ground powder is heated, sometimes under pressure, to produce a fine-grained solid material.

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120
Q

ASSEMBLED STONE

A

Two or more separate pieces of material joined to form a unit.

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121
Q

DOUBLET

A

Two separate pieces of material fused or cemented together to form a single assembled stone.

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122
Q

TRIPLET

A

A single assembled stone made from three separate pieces of material fused or cemented together, or from two pieces and a colored cement layer.

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123
Q

TREATMENTS

A

Any human-controlled process, beyond cutting and polishing, that improves the appearance, durability, or value of a gem.

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124
Q

HEAT TREATMENT

A

Exposing a gem to rising temperatures for the purpose of changing its appearance.

125
Q

OXIDIZING ENVIRONMENT

A

An oxygen-rich environment that surrounds a gem during heat treatment, causing certain color-causing trace elements to lose electrons.

126
Q

REDUCING ENVIRONMENT

A

An oxygen-poor environment that surrounds a gem during heat treatment, causing certain color-causing trace elements to gain electrons.

127
Q

GEUDA

A

Milky, grayish, or brownish corundum that can be treated to a fine blue color.

128
Q

FLUX HEALING

A

Heat treatment in the presence of a flux that results in the sealing of a fracture or cavity.

129
Q

LATTICE DIFFUSION

A

A treatment in which a gem is exposed to high temperatures and chemicals to allow penetration of color-causing elements.

130
Q

CLARITY ENHANCEMENT

A

Treatment that improves the apparent clarity of a gem with a colorless or near-colorless filler.

131
Q

FRACTURE, OR FISSURE, FILLING

A

Use of a colorless to near-colorless filler to conceal fractures and improve the apparent clarity of a gem.

132
Q

RESINS

A

A clear, viscous substance that’s used to fill fractures in gemstones.

133
Q

POLYMERS

A

A liquid filling material that’s very durable when it dries.

134
Q

HARDENER

A

A chemical that treaters mix with some resins to cause them to solidify.

135
Q

BLEACHING

A

A treatment that uses chemicals to lighten or remove color.

136
Q

COLORLESS IMPREGNATION

A

Filling of pores or other openings with melted wax, resin, polymer, or plastic to improve appearance and stability.

137
Q

DYEING

A

A treatment that adds color or affects color by deepening it, making it more even, or changing it.

138
Q

QUENCH-CRACKLING

A

A rapid heating and cooling process that produces fractures in a stone so it will accept dye.

139
Q

SURFACE MODIFICATION

A

Altering a gem’s appearance by applying backings, coatings, or coloring agents like paint.

140
Q

SUGAR TREATMENT

A

Soaking an opal in a hot sugar solution and then in sulfuric acid to darken it and bring out its play-of-color.

141
Q

SMOKE TREATMENT

A

Heating a wrapped opal until smoke or ash penetrates its surface to darken it and bring out its play-of-color.

142
Q

BENEFICIATION

A

A commitment to reserve a portion of the resources derived from any country for the economic development of that country.

143
Q

HIGH-END MARKET

A

Market sector where fine-quality, expensive gemstones are used in unique, handcrafted jewelry pieces.

144
Q

MIDDLE MARKET

A

Market sector where better-quality gemstones are used in well-finished, moderately priced jewelry pieces.

145
Q

COMMERCIAL MARKET

A

Market sector where average-quality gemstones are used in mass-market jewelry.

146
Q

CUSTOM-MADE JEWELRY

A

A unique piece designed and created for a particular customer, often around specially chosen stones.

147
Q

FREE SIZE

A

Non-standard cutting usually applied to large, important stones for use in expensive jewelry where standard size is not a consideration.

148
Q

CALIBRATED SIZES

A

Gemstone sizes cut to fit standard mountings.

149
Q

ORIGIN

A

The geographical location where a gem was mined.

150
Q

HIGH GRADING (mining)

A

In mining terms, theft of a mine’s production by its workers.

151
Q

VERTICAL INTEGRATION

A

Involvement of a business or industry in all aspects of its product’s market.

152
Q

CUTTERS

A

A manufacturer who produces faceted stones, cabochons, or carvings.

153
Q

PADPARADSCHA

A

A rare pinkish orange sapphire.

154
Q

WHOLESALER

A

A company or individual that supplies gems to jewelry manufacturers and retailers.

155
Q

PARCELS

A

A quantity of stones of similar or mixed qualities and from a single mine or various sources, that’s offered for sale together.

156
Q

CUT (selling)

A

A gem dealer’s term for a random sample from a parcel of gemstones, often used to assess the parcel’s overall quality.

157
Q

MINE LOT

A

A mixture of gem qualities that represents unsorted production from a particular mine.

158
Q

LOT PRICE

A

A discounted price for buying an entire parcel or a substantial part of it.

159
Q

GRADES

A

A specific rough gemstone quality range, usually determined by color, size, clarity, and price.

160
Q

FACET-GRADE

A

Gemstone rough that’s transparent enough and of high enough quality to produce faceted gems.

161
Q

PICK PRICE

A

A premium price for selecting stones from a parcel.

162
Q

CUTTING CENTERS

A

A city, region, or country with a large number of gemstone manufacturers.

163
Q

COLOR RANGE

A

The selection of colors in which a gemstone occurs.

164
Q

FINE COLOR

A

The color or colors in a gemstone’s color range considered by the trade to be the most desirable.

165
Q

BODYCOLOR

A

A gemstone’s basic color, determined by its selective absorption of light.

166
Q

HUE

A

The first impression of an object’s basic color.

167
Q

TONE

A

Degree of darkness or lightness of a color.

168
Q

SATURATION

A

A color’s strength or intensity.

169
Q

TRADE TERMS

A

Terms often used in the jewelry industry to describe particular gemstone colors or link gems with specific geographic locations.

170
Q

WINDOW

A

An area of weak saturation in a transparent gemstone’s bodycolor that usually results from the way the gem was cut.

171
Q

EXTINCTION

A

Dark areas in a faceted transparent colored stone.

172
Q

UNPLANNED LIGHT LEAKAGE

A

Light that exits through the pavilion in an uncontrolled way due to compromises in a gem’s proportions.

173
Q

PLANNED LIGHT LEAKAGE

A

Light that exits through a gem’s crown in a controlled way due to the correct proportions of its cut.

174
Q

COLOR ZONING

A

Areas of different color in a gem, caused by variations in growth conditions.

175
Q

UNINTENDED COLOR ZONING

A

Visible face-up color zoning that the cutter was unable to conceal.

176
Q

INTENDED COLOR ZONING

A

Visible face-up color zoning that was planned during the cutting process.

177
Q

PROPORTIONS

A

The angles and relative measurements of a polished gem, and the relationships between them.

178
Q

COBBING

A

Removing heavily included sections from gemstone rough by carefully tapping it with a small hammer.

179
Q

SAWING

A

Dividing gem rough into easily handled pieces and removing waste areas.

180
Q

GRINDING

A

Giving approximate shape to a gemstone, or producing flat planes for polishing facets.

181
Q

CROWN

A

Top part of the gem above the girdle.

182
Q

TABLE FACET

A

Facet at the top of the crown, usually the largest facet on the stone.

183
Q

PAVILION

A

Lower part of a faceted gem below the girdle.

184
Q

GIRDLE

A

Narrow section that forms the boundary between the crown and the pavilion, and functions as the gem’s setting edge.

185
Q

PREFORM

A

Rough ground to the approximate shape of the finished stone; also, the act of producing this shape.

186
Q

DOPSTICK

A

Wooden or metal stick that holds the preform during faceting.

187
Q

LAP

A

Horizontal spinning metal disk used to grind or polish a gem’s facets.

188
Q

FACETING HEAD

A

Device that holds the dopstick at precise angles to allow correct orientation during faceting and polishing.

189
Q

POLISHING

A

Final stage in gem cutting that produces the smoothest possible surface.

190
Q

STYLES

A

The arrangement of a stone’s facets.

191
Q

BRILLIANT CUT

A

Cutting style with triangular or kite-shaped facets that radiate from the center toward the girdle.

192
Q

STEP CUT

A

Cutting style with mainly square and rectangular facets arranged in concentric rows.

193
Q

MIXED CUT

A

A cutting style that combines brilliant-cut and step-cut facets.

194
Q

CABOCHONS

A

A smoothly rounded polished gem with a domed top and a flat or curved base.

195
Q

CAMEOS

A

A gem carving style in which the design, often a woman’s profile, projects slightly from a flat or curved surface.

196
Q

INTAGLIOS

A

A design engraved into the surface of a gemstone.

197
Q

DESIGNER CUTS

A

Artistic gem cuts that aren’t limited to specific proportions or shapes.

198
Q

FANTASY CUTS

A

A free-form cut that can feature alternating curved and flat surfaces.

199
Q

BRILLIANCE

A

Light that eventually returns to the eye after entering a gem through the crown, reflecting off its pavilion facets, and exiting back through the crown.

200
Q

SYMMETRY

A

The precision and balance of the corresponding parts of a finished gem.

201
Q

CROWN HEIGHT TO PAVILION DEPTH RATIO

A

The relationship of the height of a gem’s crown to the depth of its pavilion, judged by viewing its profile.

202
Q

BLEMISHES

A

Characteristic or irregularity confined to the surface of a polished gemstone.

203
Q

INCLUDED CRYSTAL

A

A mineral crystal trapped within a gem as it grows.

204
Q

NEGATIVE CRYSTALS

A

An angular, hollow space within a gem that resembles a mineral inclusion.

205
Q

NEEDLE (clarity)

A

A long, thin inclusion that can be a solid crystal or a hollow tube that might be filled with liquid or gas.

206
Q

SILK (clarity)

A

Group of fine needle-like inclusions.

207
Q

FINGERPRINT (clarity)

A

Inclusions that form a pattern that often resembles a human fingerprint.

208
Q

FEATHER (clarity)

A

A general term for a break in a stone.

209
Q

CLOUD (clarity)

A

Any hazy or milky area that cannot be described as a feather, fingerprint, or group of included crystals or needles.

210
Q

PINPOINTS (clarity)

A

Minute inclusion enclosed within a gem; can occur singly or in groups called clouds.

211
Q

CAVITY (clarity)

A

An opening that extends into a gem from the surface.

212
Q

CHIP (clarity)

A

A damaged area on a gem, usually near the girdle.

213
Q

SCRATCH

A

A linear scrape, normally seen as a fine curved or straight white line.

214
Q

ABRASIONS

A

Tiny nicks and pits caused by wear and damage to a gem’s facet edges or culet.

215
Q

POLISH LINES

A

Tiny parallel grooves on a facet surface left by the polishing operation.

216
Q

EYE-CLEAN

A

Description for a gem with no inclusions visible to the unaided eye.

217
Q

Type I stones

A

usually eye-clean, with no inclusions visible to the unaided eye. These include aquamarine; pink, green, and yellow beryl; chrysoberyl (excluding cat’s-eye); spodumene; green tourmaline; blue zircon; and tanzanite.

218
Q

Type II stones

A

typically show some eye-visible inclusions that don’t detract from the stone’s overall beauty. These include andalusite, alexandrite, corundum (excluding stars), the transparent garnets, iolite, peridot, spinel, quartz, all colors of tourmaline except green and watermelon, and zircon.

219
Q

Type III stones

A

are almost always included. Because of the environment they grow in, they frequently contain abundant inclusions of other minerals. They’re often highly fractured, and harsh mining and ­processing techniques might create more fractures, or make existing fractures larger. Type III stones include emerald, red beryl, and watermelon tourmaline.

220
Q

PER-CARAT PRICE

A

The price of a gem divided by its carat weight.

221
Q

METRIC CARATS

A

The international unit of measurement for gem weight (1 carat equals 0.20 gram).

222
Q

POINTS

A

One one-hundredth of a carat (0.01 ct.).

223
Q

UNIT PRICE

A

The price per piece.

224
Q

SIEVE SET

A

Set of circular plates, each punched with precisely sized holes, used to sort small, round gems by size.

225
Q

SCOOP

A

A small shovel made of thin metal, used for picking up gems.

226
Q

SORTING PAD

A

A neutrally colored paper pad on which dealers sort and show gems.

227
Q

MATCHING TRAY

A

A grooved, neutrally colored, non-reflective tray used to match sets of stones.

228
Q

PEARLS

A

An organic gem that forms in the body of a mollusk.

229
Q

NATURAL PEARLS

A

A pearl that forms without human assistance.

230
Q

CULTURED PEARLS

A

A pearl formed as the result of human intervention in the formation process.

231
Q

MANTLE (pearls)

A

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

232
Q

NACRE

A

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

233
Q

ARAGONITE

A

A crystallized form of calcium carbonate found in nacre.

234
Q

CONCHIOLIN

A

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

235
Q

MOTHER-OF-PEARL

A

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

236
Q

NON-NACREOUS PEARLS

A

Pearl with a non-concentric structure of aragonite crystals resulting in different luster and appearance from nacreous pearls.

237
Q

FLAME STRUCTURE (pearls)

A

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

238
Q

CULTURED BLISTER PEARLS

A

A cultured pearl grown around a nucleus implanted under the mantle tissue inside a mollusk’s shell.

239
Q

BEAD NUCLEUS

A

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

240
Q

MANTLE-TISSUE PIECE

A

A small square of mantle tissue cut from a donor mollusk and implanted in a host mollusk with or without a bead.

241
Q

GONAD

A

The reproductive organ that produces eggs in females and sperm in males.

242
Q

PEARL SAC

A

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

243
Q

AKOYA

A

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

244
Q

STRANDS

A

A simple necklace typically composed of pearls; also, pearls very close to the same size strung without a clasp for wholesale marketing.

245
Q

UNIFORM(necklace)

A

A necklace featuring pearls that are very nearly the same size.

246
Q

GRADUATED(necklace)

A

A necklace with the largest pearl in the center and progressively smaller pearls approaching the clasp.

247
Q

HATCHERY

A

A facility where biologists breed pearl-bearing mollusks in tanks under controlled conditions.

248
Q

HATCHERY-BRED

A

Describes mollusks bred in laboratory tanks and grown in protected areas rather than collected as adults in the wild.

249
Q

COIN-BEAD/SPHERICAL-BEAD (CBSB) PRODUCTION

A

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

250
Q

SECOND-GENERATION CULTURED PEARL

A

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

251
Q

HANKS

A

A number of similar cultured pearl strands bundled together.

252
Q

PROCESSORS

A

A company that prepares cultured pearls for the market.

253
Q

PROCESSES (pearls)

A

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

254
Q

VALUE FACTORS

A

Features used to judge the quality and value of pearls.

255
Q

CIRCLED PEARL

A

A pearl with one or more grooved or ridged rings all the way around it.

256
Q

Abrasion (pearls)

A

A series of scratches on the surface of a pearl

257
Q

Bump (pearls)

A

An irregular bulge, blister, or welt,usually too small to affect basic shape

258
Q

Chip (pearls)

A

An opening or cavity in the surface

259
Q

Crack (pearls)

A

A surface-reaching break or fracture in the nacre, or a break or fracture in the nucleus

260
Q

Flat (pearls)

A

A flat section on an otherwise spherical pearl, usually too small to affect basic shape

261
Q

Gap (pearls)

A

An area where the nacre has not covered the nucleus

262
Q

Pit (pearls)

A

An indentation or depression, found individually or in a group

263
Q

Scratch (pearls)

A

A thin groove or depression in the surface

264
Q

Spot (pearls)

A

An area that is darker, lighter, or more dull than the surrounding nacre

265
Q

Wrinkle (pearls)

A

An irregular ridge or crease on the surface

266
Q

FULL-DRILLED

A

Cultured pearl with a hole drilled all the way through; sometimes called drilled-through.

267
Q

HALF-DRILLED

A

Cultured pearl with a hole drilled halfway through to permit mounting on a post.

268
Q

THREE-QUARTER-CUT (pearls)

A

Cultured pearl with any unsightly portion cut or ground off.

269
Q

IMPERIAL

A

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

270
Q

MOTTLING

A

An uneven distribution of color against a contrasting background.

271
Q

OLD MINE (jade)

A

Trade term for jadeite with very fine texture.

272
Q

NEW MINE (jade)

A

Trade term for jadeite with coarse texture.

273
Q

HOLOLITH

A

Gemstone jewelry carved entirely from a single piece of rough.

274
Q

SHOW POINTS (jade)

A

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

275
Q

WINDOWS(jade)

A

A polished area on the surface of a jadeite boulder that allows the buyer to see beyond the skin.

276
Q

MUTTON-FAT JADE

A

A trade name for top-quality white nephrite.

277
Q

MOUNTAIN JADE

A

Rough nephrite extracted directly from primary deposits.

278
Q

RIVER JADE

A

Rough nephrite recovered from alluvial deposits.

279
Q

POTCH OPAL

A

Opal that lacks play-of-color.

280
Q

BACKGROUND COLOR(opal)

A

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

281
Q

MATRIX

A

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

282
Q

Black opal

A

Background color ranges from translucent to opaque black to dark gray, but should appear black in reflected light; shows play-of-color

283
Q

White opal

A

Background color ranges from translucent white to medium gray; shows play-of-color

284
Q

Crystal opal

A

Background ranges from transparent to semitransparent; shows exceptional play-of-color

285
Q

Water opal

A

Background ranges from transparent to translucent; shows faint play-of-color or no play-of-color at all

286
Q

BOULDER OPAL

A

Thin layers of precious opal, cut to include matrix.

287
Q

Fire opal

A

Background color ranges from transparent to translucent reds and oranges to yellows; might or might not show play-of-color

288
Q

Assembled opal

A

Precious opal layers, or layers of precious opal and other material, cemented together to improve durability and appearance

289
Q

Pinfire (opal)

A

Very small patches or “dots” of play-of-color

290
Q

Flash (opal)

A

Large areas of play-of-color

291
Q

Harlequin (opal)

A

Large, distinct, usually rectangular patches of play-of-color with edges touching each other

292
Q

CRAZING

A

The network of tiny fractures that develops when an opal loses moisture.

293
Q

SLOCUM STONE

A

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

294
Q

SAGENITIC QUARTZ

A

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

295
Q

RUTILATED QUARTZ

A

A type of sagenitic quartz containing needle-like rutile inclusions

296
Q

TOURMALINATED QUARTZ

A

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

297
Q

BOTRYOIDAL

A

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

298
Q

SIGNETS

A

A tablet-cut gem with a flat or slightly domed top and sometimes a carved design, typically set in men’s rings and cufflinks.

299
Q

IMPERIAL TOPAZ

A

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

300
Q

PRECIOUS TOPAZ

A

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

301
Q

ISOMORPHOUS REPLACEMENT

A

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

302
Q

HOLLOWBACK

A

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

303
Q

SPIDERWEB TURQUOISE

A

Turquoise that contains matrix in thin, web-like patterns.

304
Q

STABILIZED TURQUOISE

A

A trade term for polymer-impregnated turquoise.

305
Q

RECONSTRUCTED TURQUOISE

A

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

306
Q

BLUE SHEEN

A

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

307
Q

CENTIPEDES

A

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

308
Q

GOLDSTONE

A

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

309
Q

SUN SPANGLES

A

Circular marks sometimes left in amber when treaters heat and oil it.

GIA GEM GRADING (2 decks)

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