Definitions Flashcards
1
Q
SOURCE
A
A gem-producing country or area, or a particular mine in that area.
2
Q
INORGANIC
A
Composed of, or arising from, non-living matter.
3
Q
ORGANIC
A
Produced by, or derived from, a living organism.
4
Q
NATURAL GEMS
A
Gems produced by natural processes, without human help.
5
Q
ATOMS
A
The basic structural unit of all matter.
6
Q
CHEMICAL COMPOSITION
A
Kinds and relative quantities of atoms that make up a material.
7
Q
CHEMICAL ELEMENT
A
A substance that consists of atoms of only one kind.
8
Q
FACETS
A
A flat, polished surface on a finished gem.
9
Q
MINERALS
A
A natural, inorganic substance with a characteristic chemical composition and usually characteristic structure.
10
Q
ROCKS
A
A natural material composed of masses of mineral crystals of one or more kinds.
11
Q
SILICATES
A
A mineral that contains the elements silicon and oxygen.
12
Q
CRYSTAL STRUCTURE
A
Regular, repeating internal arrangement of atoms in a material.
13
Q
AMORPHOUS
A
Lacking a regular crystal structure.
14
Q
GEM SPECIES
A
A broad gem category based on chemical composition and crystal structure.
15
Q
VARIETY
A
A subcategory of species, based on color, transparency, or phenomenon.
16
Q
PHENOMENON
A
An unusual optical effect displayed by a gem.
17
Q
GROUP
A
A family of gems from several closely related mineral species.
18
Q
DISCLOSURE
A
Clearly and accurately informing customers about the nature of the goods they buy.
19
Q
CRUST
A
The surface and outermost layer of the earth.
20
Q
MANTLE
A
A layer between the earth’s crust and its core.
21
Q
CORE
A
The earth’s innermost layer.
22
Q
MAGMA
A
General term for any molten rock.
23
Q
PLATES
A
A section of the earth’s rigid outer crust.
24
Q
PLATE TECTONICS
A
Study of the formation, structure, and movement of the plates of the earth’s crust.
25
MANTLE CONVECTION
Circulation in the mantle that drives the movement of the earth’s plates.
26
SUBDUCTION
A process that occurs when two of the earth's plates collide, forcing one under the other.
27
OROGENIC BELTS
A long, widespread area in the earth’s crust where tectonic events cause major structural changes, often forming mountain ranges.
28
ROCK CYCLE
A constant formation and recycling process that creates new rock from old.
29
EROSION
The wearing away and transport of rock materials by natural forces.
30
IGNEOUS ROCKS
Rock formed by the crystallization of molten material.
31
METAMORPHIC ROCKS
A category of rocks that have been altered by heat and pressure.
32
SEDIMENTARY ROCKS
Rock produced from the eroded and weathered remains of existing rocks.
33
VOLCANIC
Pertaining to igneous activity at the earth’s surface, where magma erupts through a volcano or fissure.
34
PNEUMATOLYSIS
Crystallization of minerals from a gas.
35
XENOCRYST
A “foreign crystal” that forms in unrelated rocks and is brought to the surface as a passenger in magma.
36
PEGMATITES
An igneous rock typically formed from cooling, once-molten granite that follows fractures in its surrounding rock.
37
VEIN
A mineral deposit that occupies an existing fissure or fracture in the rock.
38
INTRUSION
Large mass of igneous rock that crystallizes underground without reaching the surface.
39
HYDROTHERMAL FLUID
Hot, high-pressure solution that can dissolve, transport, and deposit minerals from one place to another.
40
REGIONAL METAMORPHISM
Changes in rock type and minerals over a wide area, caused by heat and pressure of large-scale geological events.
41
CONTACT METAMORPHISM
Localized changes caused by an igneous intrusion that takes place where the magma meets the surrounding rock.
42
METASOMATISM
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.
43
GEODES
A spherical, often hollow, mineral-lined cavity in rock.
44
ARTISANAL MINERS
An independent gem or mineral prospector who typically uses small-scale, nonmechanized recovery methods.
45
OVERBURDEN
The material covering a gem deposit that must be removed before production can begin.
46
PRIMARY DEPOSIT
Gems found in the rocks that they formed in.
47
SECONDARY DEPOSITS
Gems found away from their primary source.
48
HEAVY MINERALS
Minerals dense enough to become concentrated and separated from lighter ones by the action of surface water.
49
ELUVIAL DEPOSITS
A deposit where gems are eroded from the source rock but remain in place close to the source.
50
ALLUVIAL DEPOSITS
A deposit where gems are eroded from their source rock and then transported away from the source and further concentrated.
51
PLACERS
Workable alluvial deposit of gem minerals with economic potential.
52
UNIT CELL
The smallest group of atoms with both the characteristic chemical composition and crystal structure of a mineral.
53
AGGREGATES
A mass of tiny, randomly oriented crystals.
54
MICROCRYSTALLINE
An aggregate made up of individual crystals visible under magnification.
55
CRYPTOCRYSTALLINE
An aggregate made up of individual crystals detectable only under very high magnification.
56
TWINNING
Change in a gem’s crystal direction during or after growth.
57
TWINNING PLANE
Location of a change in crystal growth direction.
58
INCLUSIONS
A characteristic enclosed within a gemstone or reaching its surface from the interior.
59
LIQUID INCLUSIONS
Small pocket in a gem that’s filled with fluids and, sometimes, gas bubbles and tiny crystals.
60
TWO-PHASE
A hollow cavity in a gem, usually filled with a liquid and a gas.
61
THREE-PHASE
A hollow cavity in a gem filled with a liquid, a gas, and one or more crystals.
62
TRACE ELEMENTS
Atoms in a gem that aren’t part of its essential chemical composition.
63
HABIT
The characteristic external crystal shape or form of a mineral.
64
DENSITY
How heavy an object is in relation to its size.
65
SPECIFIC GRAVITY
Ratio of the weight of a material to the weight of an equal volume of water.
66
DURABILITY
A gemstone’s ability to withstand wear, heat, and chemicals.
67
HARDNESS
How well a gemstone resists scratches and abrasion.
68
TOUGHNESS
How well a gemstone resists breaking and chipping.
69
CLEAVAGE
A smooth, flat break in a gemstone parallel to planes of atomic weakness, caused by weak or fewer bonds between atoms, or both.
70
PARTING
A flat break in a gemstone caused by concentrated included minerals parallel to a twinning plane.
71
FRACTURE
Any break in a gem other than cleavage or parting.
72
CONCHOIDAL FRACTURE
A curved and ridged fracture in a gemstone, extending from the surface inward.
73
STABILITY
How well a gemstone resists light, heat, and chemicals.
74
THERMAL SHOCK
Damage caused by sudden, extreme temperature changes.
75
WAVELENGTH
The distance between two adjacent high points of an energy wave.
76
SELECTIVE ABSORPTION
Process by which a material absorbs some components of visible light and transmits others.
77
ABSORPTION SPECTRUM
A pattern of dark vertical lines or bands shown by certain gems when viewed through a spectroscope.
78
TRANSITION ELEMENTS
Elements that can selectively absorb some wavelengths of visible light and produce color in gems.
79
ALLOCHROMATIC
A gem colored by trace elements in its crystal structure.
80
IDIOCHROMATIC
A gem colored by an element that is an essential part of its chemical composition.
81
CHARGE TRANSFER
The movement of electrons back and forth between ions, causing the selective absorption of light.
82
INTERVALENCE CHARGE TRANSFER.
A process where two transition elements with different valences exchange electrons to selectively absorb light.
83
COLOR CENTER
A small defect in the crystal structure of a material that can absorb light and give rise to a color.
84
IRRADIATION
Exposing a gem to manmade radiation to change or improve its color.
85
FLUORESCENCE
Emission of visible light by a material when it’s stimulated by ultraviolet or X-ray radiation.
86
PHOSPHORESCENCE
Continued emission of visible light after UV or X-ray stimulation stops.
87
REFRACTION
Change in speed and possible change in direction of light as it travels from one material to another.
88
DOUBLING
The appearance of double images of a gemstone’s facet junctions on the side opposite the viewer.
89
DOUBLE REFRACTION
When a gem’s crystal structure splits light into two rays that each travel at a slightly different speed and direction.
90
SINGLE REFRACTION
When a gem’s crystal structure doesn’t change incoming light other than by refraction and absorption.
91
OPTIC AXIS
Direction of single refraction in a doubly refractive gem.
92
PLEOCHROISM
When a gem shows different bodycolors from different crystal directions.
93
DISPERSION
The separation of white light into spectral colors.
94
INTERFERENCE
Interaction between two light rays with the same wavelengths as they travel along the same path.
95
IRIDESCENCE
A rainbow effect created when light is broken up into spectral hues by thin layers.
96
ORIENT
Iridescence seen in some natural and cultured pearls and mother-of-pearl.
97
DIFFRACTION
A special kind of interference phenomenon that produces patches of pure spectral colors.
98
PLAY-OF-COLOR
The flashing rainbow colors in opal, produced by the interaction of visible light with the gem’s microscopic internal structure of stacked silica spheres.
99
LABRADORESCENCE
A broad flash of color in labradorite feldspar that disappears when the gem is moved.
100
ADULARESCENCE
The cloudy bluish white light in a moonstone, caused by scattering of light.
101
CHATOYANCY
Bands of light in certain gems, caused by reflection of light from many parallel, needle-like inclusions or hollow tubes.
102
MILK AND HONEY
A two-toned effect seen when a chatoyant gem is positioned at right angles to a light source.
103
ASTERISM
Crossing of chatoyant bands, creating a star in the dome of a cabochon.
104
AVENTURESCENCE
A glittery effect caused by light reflecting from small, flat inclusions within a gemstone.
105
COLOR CHANGE
A distinct change in gem color under different types of lighting.
106
SYNTHETIC GEMS
A laboratory creation with essentially the same chemical composition, crystal structure, and properties as its natural counterpart.
107
IMITATION GEMS
Any material that looks like a natural gem and is used in its place.
108
MELT
A synthetic-crystal growth method in which the chemical mixture is melted and then recrystallized.
109
SOLUTION
A growth method in which the synthetic crystal grows from a dissolved chemical mixture, sometimes at high temperature and pressure.
110
FLAME FUSION
A process in which powdered chemicals are dropped through a high-temperature flame onto a rotating pedestal to produce a synthetic crystal.
111
PULLING
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.
112
BOULE
A cylindrical synthetic crystal produced by a melt process.
113
SEED CRYSTAL
A tiny crystal used as a template to control the size, speed, or direction of growth and the shape of a growing synthetic crystal.
114
FLOATING ZONE
A melt process where a heating unit passes over a rotating solid rod of chemicals until it forms a synthetic crystal.
115
SKULL MELT
A synthetic-crystal growth method that uses cooling pipes around an interior of melted chemical ingredients.
116
FLUX GROWTH
A process in which nutrients dissolve in heated chemicals, then cool to form synthetic crystals.
117
HYDROTHERMAL GROWTH
A process in which nutrients dissolve in a water solution at high temperature and pressure, then cool to form synthetic crystals.
118
SPONTANEOUS NUCLEATION
A synthetic-crystal growth method that starts without a seed crystal.
119
CERAMIC PROCESSES
A process in which finely ground powder is heated, sometimes under pressure, to produce a fine-grained solid material.
120
ASSEMBLED STONE
Two or more separate pieces of material joined to form a unit.
121
DOUBLET
Two separate pieces of material fused or cemented together to form a single assembled stone.
122
TRIPLET
A single assembled stone made from three separate pieces of material fused or cemented together, or from two pieces and a colored cement layer.
123
TREATMENTS
Any human-controlled process, beyond cutting and polishing, that improves the appearance, durability, or value of a gem.
124
HEAT TREATMENT
Exposing a gem to rising temperatures for the purpose of changing its appearance.
125
OXIDIZING ENVIRONMENT
An oxygen-rich environment that surrounds a gem during heat treatment, causing certain color-causing trace elements to lose electrons.
126
REDUCING ENVIRONMENT
An oxygen-poor environment that surrounds a gem during heat treatment, causing certain color-causing trace elements to gain electrons.
127
GEUDA
Milky, grayish, or brownish corundum that can be treated to a fine blue color.
128
FLUX HEALING
Heat treatment in the presence of a flux that results in the sealing of a fracture or cavity.
129
LATTICE DIFFUSION
A treatment in which a gem is exposed to high temperatures and chemicals to allow penetration of color-causing elements.
130
CLARITY ENHANCEMENT
Treatment that improves the apparent clarity of a gem with a colorless or near-colorless filler.
131
FRACTURE, OR FISSURE, FILLING
Use of a colorless to near-colorless filler to conceal fractures and improve the apparent clarity of a gem.
132
RESINS
A clear, viscous substance that’s used to fill fractures in gemstones.
133
POLYMERS
A liquid filling material that’s very durable when it dries.
134
HARDENER
A chemical that treaters mix with some resins to cause them to solidify.
135
BLEACHING
A treatment that uses chemicals to lighten or remove color.
136
COLORLESS IMPREGNATION
Filling of pores or other openings with melted wax, resin, polymer, or plastic to improve appearance and stability.
137
DYEING
A treatment that adds color or affects color by deepening it, making it more even, or changing it.
138
QUENCH-CRACKLING
A rapid heating and cooling process that produces fractures in a stone so it will accept dye.
139
SURFACE MODIFICATION
Altering a gem’s appearance by applying backings, coatings, or coloring agents like paint.
140
SUGAR TREATMENT
Soaking an opal in a hot sugar solution and then in sulfuric acid to darken it and bring out its play-of-color.
141
SMOKE TREATMENT
Heating a wrapped opal until smoke or ash penetrates its surface to darken it and bring out its play-of-color.
142
BENEFICIATION
A commitment to reserve a portion of the resources derived from any country for the economic development of that country.
143
HIGH-END MARKET
Market sector where fine-quality, expensive gemstones are used in unique, handcrafted jewelry pieces.
144
MIDDLE MARKET
Market sector where better-quality gemstones are used in well-finished, moderately priced jewelry pieces.
145
COMMERCIAL MARKET
Market sector where average-quality gemstones are used in mass-market jewelry.
146
CUSTOM-MADE JEWELRY
A unique piece designed and created for a particular customer, often around specially chosen stones.
147
FREE SIZE
Non-standard cutting usually applied to large, important stones for use in expensive jewelry where standard size is not a consideration.
148
CALIBRATED SIZES
Gemstone sizes cut to fit standard mountings.
149
ORIGIN
The geographical location where a gem was mined.
150
HIGH GRADING (mining)
In mining terms, theft of a mine’s production by its workers.
151
VERTICAL INTEGRATION
Involvement of a business or industry in all aspects of its product’s market.
152
CUTTERS
A manufacturer who produces faceted stones, cabochons, or carvings.
153
PADPARADSCHA
A rare pinkish orange sapphire.
154
WHOLESALER
A company or individual that supplies gems to jewelry manufacturers and retailers.
155
PARCELS
A quantity of stones of similar or mixed qualities and from a single mine or various sources, that’s offered for sale together.
156
CUT (selling)
A gem dealer’s term for a random sample from a parcel of gemstones, often used to assess the parcel’s overall quality.
157
MINE LOT
A mixture of gem qualities that represents unsorted production from a particular mine.
158
LOT PRICE
A discounted price for buying an entire parcel or a substantial part of it.
159
GRADES
A specific rough gemstone quality range, usually determined by color, size, clarity, and price.
160
FACET-GRADE
Gemstone rough that’s transparent enough and of high enough quality to produce faceted gems.
161
PICK PRICE
A premium price for selecting stones from a parcel.
162
CUTTING CENTERS
A city, region, or country with a large number of gemstone manufacturers.
163
COLOR RANGE
The selection of colors in which a gemstone occurs.
164
FINE COLOR
The color or colors in a gemstone’s color range considered by the trade to be the most desirable.
165
BODYCOLOR
A gemstone’s basic color, determined by its selective absorption of light.
166
HUE
The first impression of an object’s basic color.
167
TONE
Degree of darkness or lightness of a color.
168
SATURATION
A color’s strength or intensity.
169
TRADE TERMS
Terms often used in the jewelry industry to describe particular gemstone colors or link gems with specific geographic locations.
170
WINDOW
An area of weak saturation in a transparent gemstone’s bodycolor that usually results from the way the gem was cut.
171
EXTINCTION
Dark areas in a faceted transparent colored stone.
172
UNPLANNED LIGHT LEAKAGE
Light that exits through the pavilion in an uncontrolled way due to compromises in a gem’s proportions.
173
PLANNED LIGHT LEAKAGE
Light that exits through a gem’s crown in a controlled way due to the correct proportions of its cut.
174
COLOR ZONING
Areas of different color in a gem, caused by variations in growth conditions.
175
UNINTENDED COLOR ZONING
Visible face-up color zoning that the cutter was unable to conceal.
176
INTENDED COLOR ZONING
Visible face-up color zoning that was planned during the cutting process.
177
PROPORTIONS
The angles and relative measurements of a polished gem, and the relationships between them.
178
COBBING
Removing heavily included sections from gemstone rough by carefully tapping it with a small hammer.
179
SAWING
Dividing gem rough into easily handled pieces and removing waste areas.
180
GRINDING
Giving approximate shape to a gemstone, or producing flat planes for polishing facets.
181
CROWN
Top part of the gem above the girdle.
182
TABLE FACET
Facet at the top of the crown, usually the largest facet on the stone.
183
PAVILION
Lower part of a faceted gem below the girdle.
184
GIRDLE
Narrow section that forms the boundary between the crown and the pavilion, and functions as the gem’s setting edge.
185
PREFORM
Rough ground to the approximate shape of the finished stone; also, the act of producing this shape.
186
DOPSTICK
Wooden or metal stick that holds the preform during faceting.
187
LAP
Horizontal spinning metal disk used to grind or polish a gem’s facets.
188
FACETING HEAD
Device that holds the dopstick at precise angles to allow correct orientation during faceting and polishing.
189
POLISHING
Final stage in gem cutting that produces the smoothest possible surface.
190
STYLES
The arrangement of a stone’s facets.
191
BRILLIANT CUT
Cutting style with triangular or kite-shaped facets that radiate from the center toward the girdle.
192
STEP CUT
Cutting style with mainly square and rectangular facets arranged in concentric rows.
193
MIXED CUT
A cutting style that combines brilliant-cut and step-cut facets.
194
CABOCHONS
A smoothly rounded polished gem with a domed top and a flat or curved base.
195
CAMEOS
A gem carving style in which the design, often a woman’s profile, projects slightly from a flat or curved surface.
196
INTAGLIOS
A design engraved into the surface of a gemstone.
197
DESIGNER CUTS
Artistic gem cuts that aren’t limited to specific proportions or shapes.
198
FANTASY CUTS
A free-form cut that can feature alternating curved and flat surfaces.
199
BRILLIANCE
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
SYMMETRY
The precision and balance of the corresponding parts of a finished gem.
201
CROWN HEIGHT TO PAVILION DEPTH RATIO
The relationship of the height of a gem’s crown to the depth of its pavilion, judged by viewing its profile.
202
BLEMISHES
Characteristic or irregularity confined to the surface of a polished gemstone.
203
INCLUDED CRYSTAL
A mineral crystal trapped within a gem as it grows.
204
NEGATIVE CRYSTALS
An angular, hollow space within a gem that resembles a mineral inclusion.
205
NEEDLE (clarity)
A long, thin inclusion that can be a solid crystal or a hollow tube that might be filled with liquid or gas.
206
SILK (clarity)
Group of fine needle-like inclusions.
207
FINGERPRINT (clarity)
Inclusions that form a pattern that often resembles a human fingerprint.
208
FEATHER (clarity)
A general term for a break in a stone.
209
CLOUD (clarity)
Any hazy or milky area that cannot be described as a feather, fingerprint, or group of included crystals or needles.
210
PINPOINTS (clarity)
Minute inclusion enclosed within a gem; can occur singly or in groups called clouds.
211
CAVITY (clarity)
An opening that extends into a gem from the surface.
212
CHIP (clarity)
A damaged area on a gem, usually near the girdle.
213
SCRATCH
A linear scrape, normally seen as a fine curved or straight white line.
214
ABRASIONS
Tiny nicks and pits caused by wear and damage to a gem’s facet edges or culet.
215
POLISH LINES
Tiny parallel grooves on a facet surface left by the polishing operation.
216
EYE-CLEAN
Description for a gem with no inclusions visible to the unaided eye.
217
Type I stones
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
Type II stones
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
Type III stones
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
PER-CARAT PRICE
The price of a gem divided by its carat weight.
221
METRIC CARATS
The international unit of measurement for gem weight (1 carat equals 0.20 gram).
222
POINTS
One one-hundredth of a carat (0.01 ct.).
223
UNIT PRICE
The price per piece.
224
SIEVE SET
Set of circular plates, each punched with precisely sized holes, used to sort small, round gems by size.
225
SCOOP
A small shovel made of thin metal, used for picking up gems.
226
SORTING PAD
A neutrally colored paper pad on which dealers sort and show gems.
227
MATCHING TRAY
A grooved, neutrally colored, non-reflective tray used to match sets of stones.
228
PEARLS
An organic gem that forms in the body of a mollusk.
229
NATURAL PEARLS
A pearl that forms without human assistance.
230
CULTURED PEARLS
A pearl formed as the result of human intervention in the formation process.
231
MANTLE (pearls)
The organ that lines the mollusk’s shell, encloses its soft body, and contains the cells that form pearl sacs and secrete nacre.
232
NACRE
The natural substance produced by pearl-bearing mollusks to make pearls.
233
ARAGONITE
A crystallized form of calcium carbonate found in nacre.
234
CONCHIOLIN
The organic “glue” in nacre that holds aragonite platelets together.
235
MOTHER-OF-PEARL
The nacreous layer inside a pearl-bearing mollusk’s shell.
236
NON-NACREOUS PEARLS
Pearl with a non-concentric structure of aragonite crystals resulting in different luster and appearance from nacreous pearls.
237
FLAME STRUCTURE (pearls)
Optical phenomenon created in some non-nacreous pearls when intersecting groups of crystals interact with light.
238
CULTURED BLISTER PEARLS
A cultured pearl grown around a nucleus implanted under the mantle tissue inside a mollusk’s shell.
239
BEAD NUCLEUS
A bead used as the core of a cultured pearl, usually made from a freshwater mussel shell.
240
MANTLE-TISSUE PIECE
A small square of mantle tissue cut from a donor mollusk and implanted in a host mollusk with or without a bead.
241
GONAD
The reproductive organ that produces eggs in females and sperm in males.
242
PEARL SAC
Tissue that encloses an implanted bead nucleus and mantle-tissue piece, or the piece alone, and secretes nacre to form a cultured pearl.
243
AKOYA
Common name for the Pinctada fucata oyster and the natural or cultured pearls it produces.
244
STRANDS
A simple necklace typically composed of pearls; also, pearls very close to the same size strung without a clasp for wholesale marketing.
245
UNIFORM(necklace)
A necklace featuring pearls that are very nearly the same size.
246
GRADUATED(necklace)
A necklace with the largest pearl in the center and progressively smaller pearls approaching the clasp.
247
HATCHERY
A facility where biologists breed pearl-bearing mollusks in tanks under controlled conditions.
248
HATCHERY-BRED
Describes mollusks bred in laboratory tanks and grown in protected areas rather than collected as adults in the wild.
249
COIN-BEAD/SPHERICAL-BEAD (CBSB) PRODUCTION
A three-step freshwater cultivation process involving a series of distinct growth periods.
250
SECOND-GENERATION CULTURED PEARL
Product that results when a pearl-bearing mollusk is returned to the water after the first harvest.
251
HANKS
A number of similar cultured pearl strands bundled together.
252
PROCESSORS
A company that prepares cultured pearls for the market.
253
PROCESSES (pearls)
A procedure that includes cleaning, buffing, and sometimes bleaching, done to make cultured pearls presentable and appealing.
254
VALUE FACTORS
Features used to judge the quality and value of pearls.
255
CIRCLED PEARL
A pearl with one or more grooved or ridged rings all the way around it.
256
Abrasion (pearls)
A series of scratches on the surface of a pearl
257
Bump (pearls)
An irregular bulge, blister, or welt, usually too small to affect basic shape
258
Chip (pearls)
An opening or cavity in the surface
259
Crack (pearls)
A surface-reaching break or fracture in the nacre, or a break or fracture in the nucleus
260
Flat (pearls)
A flat section on an otherwise spherical pearl, usually too small to affect basic shape
261
Gap (pearls)
An area where the nacre has not covered the nucleus
262
Pit (pearls)
An indentation or depression, found individually or in a group
263
Scratch (pearls)
A thin groove or depression in the surface
264
Spot (pearls)
An area that is darker, lighter, or more dull than the surrounding nacre
265
Wrinkle (pearls)
An irregular ridge or crease on the surface
266
FULL-DRILLED
Cultured pearl with a hole drilled all the way through; sometimes called drilled-through.
267
HALF-DRILLED
Cultured pearl with a hole drilled halfway through to permit mounting on a post.
268
THREE-QUARTER-CUT (pearls)
Cultured pearl with any unsightly portion cut or ground off.
269
IMPERIAL
Trade name for finest-quality, semitransparent jadeite with even, vivid green coloration.
270
MOTTLING
An uneven distribution of color against a contrasting background.
271
OLD MINE (jade)
Trade term for jadeite with very fine texture.
272
NEW MINE (jade)
Trade term for jadeite with coarse texture.
273
HOLOLITH
Gemstone jewelry carved entirely from a single piece of rough.
274
SHOW POINTS (jade)
Spots of color near the surface of a jadeite boulder, where the skin is thin enough to allow color to show through.
275
WINDOWS(jade)
A polished area on the surface of a jadeite boulder that allows the buyer to see beyond the skin.
276
MUTTON-FAT JADE
A trade name for top-quality white nephrite.
277
MOUNTAIN JADE
Rough nephrite extracted directly from primary deposits.
278
RIVER JADE
Rough nephrite recovered from alluvial deposits.
279
POTCH OPAL
Opal that lacks play-of-color.
280
BACKGROUND COLOR(opal)
An opal’s bodycolor, independent of its play-of-color.
281
MATRIX
A gem material’s host rock, which sometimes becomes part of the finished gem.
282
Black opal
Background color ranges from translucent to opaque black to dark gray, but should appear black in reflected light; shows play-of-color
283
White opal
Background color ranges from translucent white to medium gray; shows play-of-color
284
Crystal opal
Background ranges from transparent to semitransparent; shows exceptional play-of-color
285
Water opal
Background ranges from transparent to translucent; shows faint play-of-color or no play-of-color at all
286
BOULDER OPAL
Thin layers of precious opal, cut to include matrix.
287
Fire opal
Background color ranges from transparent to translucent reds and oranges to yellows; might or might not show play-of-color
288
Assembled opal
Precious opal layers, or layers of precious opal and other material, cemented together to improve durability and appearance
289
Pinfire (opal)
Very small patches or “dots” of play-of-color
290
Flash (opal)
Large areas of play-of-color
291
Harlequin (opal)
Large, distinct, usually rectangular patches of play-of-color with edges touching each other
292
CRAZING
The network of tiny fractures that develops when an opal loses moisture.
293
SLOCUM STONE
A manmade glass opal imitation with scattered, tinsel-like colored flakes that imitate play-of-color.
294
SAGENITIC QUARTZ
Transparent quartz, usually rock crystal, that contains eye-visible inclusions, often named according to the type of inclusions it contains.
295
RUTILATED QUARTZ
A type of sagenitic quartz containing needle-like rutile inclusions
296
TOURMALINATED QUARTZ
A type of sagenitic quartz containing needle-like or rod-like tourmaline inclusions.
297
BOTRYOIDAL
A crystal growth habit with a bumpy appearance similar to a bunch of grapes.
298
SIGNETS
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
IMPERIAL TOPAZ
A widely used trade term for gem-quality topaz of medium reddish orange to orange-red color.
300
PRECIOUS TOPAZ
A trade term for orange-to-yellow and brown topaz.
301
ISOMORPHOUS REPLACEMENT
Substitution of one chemical element for another in the crystal structure of a mineral.
302
HOLLOWBACK
A cabochon with a curved, undercut bottom, designed to lighten the tone of the gem material.
303
SPIDERWEB TURQUOISE
Turquoise that contains matrix in thin, web-like patterns.
304
STABILIZED TURQUOISE
A trade term for polymer-impregnated turquoise.
305
RECONSTRUCTED TURQUOISE
A turquoise imitation made of a mixture of powdered minerals, dyed and bonded with plastic or epoxy resin.
306
BLUE SHEEN
Trade term for a highly prized, vivid blue adularescence displayed by the finest moonstone.
307
CENTIPEDES
Tiny tension cracks in moonstone that interfere with adularescence and reduce value.
308
GOLDSTONE
An imitation of aventurine feldspar made of glass that contains small copper crystals.
309
SUN SPANGLES
Circular marks sometimes left in amber when treaters heat and oil it.
