Glossary:                                                   
                                       (Associations, Institutes, Organisms, Laboratories, Titles of Study…etc)
 
·  ACAM: Academie voor Mineralogie 
·  ACA: American Crystallographic Association
·  AGA: Accredited Gemologists Association
·  AGL: American Gemological Laboratories 
·  AGTA-GTC:  American Gem Trade Association-Gemological Testing Center 
·  AJA:  Applied Jeweler Arts 
·  AJP: Accredited Jewelry Professional 
·  ATC’s: Allied Teaching Centers
·  AWDC: Antwerp World Diamond Centre
·  BJA: British Jewellers Association 
·  BSc (Hon): Bachelor of Science (Honours Degree)
·  CAAJ-ZENHOKYO: Gemmological Association of All Japan 
·  CAP-CJA: Certified Appraisal Professional-Canada Jewellers Assiociation
·  CDG:  Certified Diamond Grader, graduate 
·  CGA: Canadian Gemmological Association 
·  CNMMN: Commission on New Minerals and Mineral Names 
·  CIG: Collegio Italiano Gemmologi
·  CIJT:  California Institute of Jewelry Training
·  DCLA: Diamond Certification Laboratory of Australia
·  DEF: Diamond Empowerment Fund  (Μη Κερδοσκοπικός Οργανισμός που φροντίζει την εκπαίδευση των παιδιών της Αφρικής) 
·  DGA: 
·  DGI: Dutch Gemmological Institute 
·  DTC: Diamond Trading Company 
·  DTSC: Department of Toxic Substance Control 
·  ECM: European Crystallographic Meeting 
·  EGL USA: European Gemological Laboratory USA
·  EGUB: Escola de Gemmologia de la Universitat de Barcelona 
·  FCGmA:  Gemmologist, graduate 
·  FEEG: Federation for European Education in Gemmology 
·  FGA:  Fellow, Gemmological Association (of Great Britain)
·  GAA: Gemmological Association of Australia
·  GAGTL: Gemmological Association and Gem Testing Laboratory of Great Britain
·  GAHK: Gemmological Association of Hong Kong
·  GANZ: Gemmological Association of New Zealand
·  GASL: Gemmologists Association of Sri Lanka
·  GCAL: Gem Certification and Assurance Laboratory
·  GCI: Gemological Center Inc Israel
·  GCS: Graduate Colored Stones
·  GD:  Graduate Diamonds
·  GG: Graduate Gemologist
·  GIA: Gemological Institute of America
·  GII: Gemmological Institute of India
·  GJ:   Graduate Jeweler
·  GP:  Graduate Pearls
·  GREGA:  Greek Researching Educational Gemmological Association
·  GTC:  Gemological Testing Center
·  GTLA: Gem Testing Laboratoty Athens ATC
·  HRD: Hoge Raad voor Diamant (Institute of Gemmology/Antwerp)
·  IDI: Israel Diamond Institute
·  IGA: Italian Gemmologists Association
·  IGE: Instituto Gemologico Espanol
·  IGI: International Gemmological Institute
·  IGI: Istituto Gemmologico Italiano
·  IMA: International Mineralogical Association
·  ING: Institut National de Gemmologic
·  IUCr: International Union of Crystallography
·  ISG: International School Gemology
·  JBM:  Jewelry Business Management
·  JCOC: Jewelry Consumer Opinion Council
·  LFG: Laboratorie Francais de Gemmologie
·  LMHC: Laboratory Manual Harmonisation Committee
·  MAF:   Master of Fine Arts
·  MSc: Master of Science
·  NEL: Nederlands Edelsteen Laboratium (Netherlands Gemmological Laboratory)
·  NRC: Nuclear Regulatory Commission  (Επιτροπή Ατομικής Ενέργειας (USA)/Έλεγχος ραδιενεργής ακτινοβολίας σε πολύτιμους λίθους)
·  PAI: Palladium Alliance International
·  PGI: Platinum Guild International
·  PGJD: Pakistan Gems and Jewelry Development.Co
·  RJC: Responsible Jewellery Council
·  RMV:  Registered Master Valuer, graduate
·  RUM: Russian University of Mineralogy
·  SBG: Societe Belge de Gemmologie
·  SGG: Schweizerische Gemmologische Gesellshaft
·  SSEF: Schweizerische Stiftung für Edelstein-Forschung (Swiss Gemmological Institute)
·  SSG: Societe Suisse de Gemmologie
·  WDL: Williamson Diamonds Limited (Κοινοπραξία μεταξύ της Κυβέρνησης της Τανζανίας και της De Beers)
·  WFDB: World Federation of Diamond Bourses
·  WFDB: World Federation of Diamond Bourses
·  WGI: World Gemological Institute
·  ΒΕΑ:  Βιοτεχνικό Επιμελητήριο Αθηνών
·  ΓΣΕΒΕΕ: Γενική Συνομοσπονδία Επαγγελματιών Βιοτεχνών Εμπόρων Ελλάδας
·  ΕΛΚΑ: Ελληνικό Κέντρο Αργυροχρυσοχοίας
·  ΕΟΜΜΕΧ: Ελληνικός Οργανισμός Μικρών-Μεσαίων Επιχειρήσεων και Χειροτεχνείας
·  ΕΣΠΑ: Εθνικό Στρατηγικό Πλαίσιο Αναφοράς
·  ΚΠΑ: Κέντρο Προώθησης Απασχόλησης
·  ΙΓΜΕ: Ινστιτούτο Γεωλογικών και Μεταλλευτικών Ερευνών
·  ΠΟΒΑΚΟ: Πανελλήνια Ομοσπονδία Βιοτεχνών Αργυροχρυσοχόων Κοσμηματοπολών Ωρολογοπωλών
·  ΣΑΑ: Σύλλογος Αργυροχρυσόχοων Αθηνών
·  ΣΒΑ: Σύνδεσμος Βιοτεχνών Αργυροχρυσοχόων
·  ΣΚΩΘ: Σύλλογος Κοσμηματοπωλών-Ωρογοπωλών Θεσσαλονίκης
·  ΣΧΑΘ: Συντεχνία Χρυσοχόων-Αργυροχρυσοχόων Θεσσαλονίκης  

                                                                                 ...Written (2009)….. By George K.Kiamos FGA, DGA ... 

                              Gemmology and Jewellery Glossary

A:

ABSORPTION SPECTRUM - The absorption of certain wavelengths of light causing dark lines or gaps in the visible spectrum.

ACICULAR - Thin, elongated, needle-like crystal inclusions.

ADULARESCENCE - The appearance of a floating, billowy light in some cabochons such as moonstone.

AIGRETTE - An ornament worn in the hair or on a cap, often set with pearls or gems, that was popular in the middle of the eighteenth century and the early twentieth century. Often a tuft of upright plumes, especially the tail feathers of an egret.

ALLOY - A metal such as copper, nickel or zinc (among others) which is added to precious metals, to provide strength and colour variety. 
Copper added to gold makes rose gold while nickel added to gold produces white gold.

AMORPHOUS - A material that has no crystal structure, no regular arrangement of its atoms,

ANNEALING - The process of heating metal and then cooling, either slowly or by quenching, to make it more pliable.

ANISOTROPIC - A gemstone possessing the property of double refraction.

ASTERISM - The optical phenomenon of a rayed figure in the form of a star. The star may be 4-ray, 6-ray (most common) or the rarely seen 12-ray. Asterism is caused by the reflection of light from minute oriented and aligned needle-like inclusions.

AKOYA OYSTERS - The most important mollusk in the cultivation of saltwater pearls.

ALLUVIAL DEPOSITS - Gems deposited by a stream, river, or running water away from the original source.

A JOUR - An opening in the setting that leaves the pavilion facets open.

ART DECO - A streamlined, geometric style of architecture, home furnishings and jewelry characterized by geometric lines and angular shapes, zigzags, bold colours, plastics (such as Bakelite) and chrome. Colored stones such as jade and onyx and were often set in geometric shapes.

ART NOUVEAU - A period of design between the 1890's and 1910; the jewelry is characterized by flowing lines, 
unusual interpretations of nature and the utilization of unusual materials

ASSAYING - The process of determining the amount of precious metal contained in a specimen.

AVENTURESCENCE - A glittery appearance on the surface of a gemstone caused
by the reflection of light off small mineral inclusions or platelets. Aventurine quartz is one obvious example.

B:

BAGUETTE - A rectangular or tapered style of step cut used for small gem materials, most often diamonds.

BAKELITE - Trade name for the first moldable, synthesized plastic, invented early in the Twentieth Century by Dr. Leo Backeland. 
Used extensively during the depression of the 1930's to make jewelry and many other items.

BAROQUE - Irregular in shape. Most often associated with pearls but can also refer to tumbled stones or freeform shaped gem materials.

BASE METAL - Any non-porous metal which is often electroplated or bonded with gold.

BASSE-TAILLE - A technique of enameling in which the surface of the metal is hollowed out and overlaid with translucent enamel.
 An extension of the champleve process.

BEAD - A drilled stone designed to be strung.

BEZEL - A type of setting where the girdle of the stone is completely covered by the metal.

BEZEL FACET - The kite shaped facet on the crown of a brilliant cut stone. 
There are eight bezel facets on the standard round brilliant cut.

BIAXIAL - Having two optic axes of single refraction in a doubly refractive gem.
 Only gems from the orthorhombic, monoclinic or triclinic crystal systems are biaxial.

BIREFRINGENCE - The measure of the difference between the highest refractive index and the lowest refractive index of a doubly refractive stone.

BIWA PEARL - Freshwater cultured pearls from Lake Biwa in Japan.

BLEMISH - Any surface imperfection on the surface of a gemstone or pearl. 
These include nicks, knots, pits, scratches, abrasions, abraded facet junctions, polish lines, minor cracks or fissures or a poor polish.

BLISTER PEARL - An irregularly shaped, hollow pearl cut from the inside surface of a mollusk's shell, 
that it is dome-shaped on one side and flattened on the other.

"BLUE-WHITE" - A term which should not be used anymore. According to the Federal Trade Commission, 
only diamonds with a distinct blue body color may be traded as "blue-white." 
 For many years the term referred to a diamond without a distinctive body color. 
Misuse of this term has rendered it meaningless.

BRASS - An alloy of copper and zinc. Yellow brass has 65% copper and 35% zinc.

BRILLIANCE - The total amount of white light returned to the eye from a diamond or colored stone as the result of internal and external reflections. Refractive index, proportions, polish, symmetry and transparency are the major factors that affect the amount of brilliance in a gem.

BRILLIANT CUT - The most common style of diamond cutting. Has the table, 32 facets above the girdle,
 24 facets below the girdle and sometimes the culet. The round brilliant cut features 57 facets without the culet or 58 facets with the culet.

BRIOLETTE - A tear-drop shaped stone, sometimes pierced at the top, without a table, that has facets all the way around. 
 Also known as drop-cut, this type of cut makes a nice pendant or pair of earrings.

BRONZE - A metal alloy containing 8 parts copper to 1 part tin.

  

BOULE - A pear or carrot shaped rough form of flame fusion synthetic corundum or spinel. Must be split to relieve strain before being cut into gems.

BOX CHAIN - A chain with square links resembling small overlapping boxes.

BYPASS SHANK - A ring design in which the two sides of the band do not meet but pass by one another.

C:

CABOCHON CUT - A rounded gem, without facets, polished into a dome shape.

CALIBRATED GEM - Gemstones with standard dimensions and shapes to fit ready made findings or mountings.

CALIPERS - An fine instrument used for measuring of both the outside and inside surfaces of a stone or mounting.

CARBUNCLE - An almandine garnet cut en cabochon.

CAMEO - A carved shell or other material, usually with colored layers, cut into a raised or bas-relief form.

CANARY - A term referring to diamonds with an intense yellow hue which is beyond Z in the GIA diamond color grading scale. 
Also called fancy yellow.

CANNETILLE - A wirework decoration of gold or silver filigree with fine twisted wires forming a coiled spiral to achieve a delicate scrolling effect. 
Used in early nineteenth century jewelry during the Georgian period.

CARAT - The term used to denote the weight of gemstones. Equals 100 points, 200 milligrams or 1/5 of a gram (0.200 grams).

CASTING - The method that uses a wax pattern from which an investment mold is made. The investment is heated and the wax melts away (or is "lost") and the metal is poured or injected into the form where the wax once was. Also known as "lost wax casting."

CAT'S EYE - An optical phenomena which shows a thin bright line across the gem. A form of chatoyancy, these gems are always cut en cabochon.

Champlevé - a technique of enameling where the enamel is placed in stamped, cut or engraved recesses of the metal.

CHANNEL SETTING - A row of stones, generally of the same size, that are set into a metal channel.

CHASING - The technique of working a design into the front surface of a metal using a hammer and/or punches

CHATELAINE - An ornamental chain, pin or clasp, usually worn at a woman's waist, from which various implements are suspended.

CHATOYANCY - The optical phenomena of a silky, broad band of light across a stone's surface which moves
 as the stone or light source is moved. Certain stones with chatoyancy display a "cat's-eye" effect,
 a thin bright line across the gem when cut properly. 
These gems are always cut en cabochon. Some stones such as tiger's eye show broad bands of chatoyancy.

CHOKER LENGTH - A strand of pearls 15" in length, worn high on the neck.

CLARITY ENHANCEMENT - Also called fracture filling, a gemstone, usually a diamond, is treated
 to improve its appearance by filling fissures or fractures with a transparent, glassy substance.

CLARITY GRADE - One of the four value factors of a diamond or colored stone. Diamonds are ranked on a scale from flawless
 (no inclusions visible under 10x magnification) to included (eye visible inclusions). 
The grades are Fl, IF, VVS-1, VVS-2, VS-1, VS-2, SI-1, SI-2, I-1, I-2 and I-3.

CLEAVAGE - The tendency of a crystalline mineral to break in certain definite directions,
 connected to its atomic structure, called cleavage planes.
 A diamond can be split by cleaving, a process where a stone is studied so that the plane
 may be defined and divided with a swift blow. 
This swift blow splits the stone into proportions quickly as opposed to sawing.
 Ironically, gems defined as having perfect cleavage are the ones most likely to break when being cut or faceted.

Cloisonné - A technique of enameling in which the piece is shaped by soldering wire or thin strips of metal
 to a metal backing with the enamel held in small cells.

COLOR - A property used in the evaluation of a gem. In diamonds, the less color the higher the value index while in colored stones,
 the more color the higher the value index.

COLOR CHANGE - An optical phenomenon of some colored stones in which the gem appears as a different color under different types of light.
 Caused by selective absorption and/or transmission of the specific type of light to which the gemstone is exposed.

COLORED STONE - Any natural gemstone excluding diamonds.

COLOR GRADE - One of the four value factors of a diamond. Diamonds are ranked on a scale from "D" (colourless) to "Z" 
(noticeable tint of color, typically yellow or brown). Diamonds with saturation greater than "Z" color 
are considered Fancy Colored Diamonds and are graded on a separate scale. 
The colors D, E and F are all colourless, differing very slightly in transparency.

COLOUR ORIGIN - The determination of the cause of color in fancy colored diamonds. 
Naturally colored diamonds are very rare and expensive.
 The two most common ways of enhancing the color of diamonds are irradiation and the high pressure high temperature (HPHT) process.

CONCHIOLIN - The dark substance secreted by a mollusk for protection which is the beginning of the cultivation of pearls.
 Nacre will cover the conchiolin for the final finish on the pearl.

CONCHOIDAL - The most common type of fracture where the surface resembles a clamshell. Common is glass and most gemstones.

CRITICAL ANGLE - When measured from the normal, the largest angle from which light can escape 
from a gemstone and the smallest angle to the normal from which light is totally reflected within the gemstone.

CROWN - The top portion of a faceted gem which is above the girdle.

CRYPTOCRYSTALLINE - Crystals so small that they cannot be resolved by an ordinary microscope. 
The effect on polarized light is the method of detection.

CRYSTAL SYSTEM - One of the seven systems in which the patterns of atoms are arranged in space to form minerals. 
The six systems most gemologists use are isometric (cubic), tetragonal, orthorhombic, monoclinic, triclinic and hexagonal.
 The seventh system, trigonal, is sometimes treated as a subdivision of the hexagonal system.

CULET - The small facet polished at the very tip of the pavilion of a diamond. It was cut to avoid breaking this tip.

CULTURED PEARL- A pearl produced by the human implantation of a nucleus, usually a shell bead or mantle tissue,
 into the body of a pearl bearing mollusk. 

CUBIC - One of the seven crystal systems in gemmology. 
Having a cube shape. Also known as the isometric crystal system.

D:

DEMI-PARURE - A small suite (two pieces) of matching jewelry, consisting of a brooch and earrings, 
a necklace and bracelet, necklace and earrings or some other matching pair.

DENSITY - Mass per volume unit; approximates specific gravity.

DIAMOND-CUT - A process to bright cut gold jewelry using a diamond embedded cutting tool.

DICHROISM - The ability of some doubly refractive gems to display a second color when viewed from a different angle.
 Easiest seen with a dichroscope.

DICHROSCOPE - A small instrument used in gem identification to detect pleochroism in doubly refractive gems.

DIFFUSION - The process of enhancing the color of a stone by heating it in the presence of iron oxide, chrome oxide or similar compounds.
 The treatment is only done on stones already cut because it only colors the surface. Recutting will remove the treatment.
 Often used on sapphires and topaz to increase or change the colors.

DISPERSION - The separation of white light into its component spectral colors. 
Sometimes called fire, it is the difference in the gem's refractive index for red light and blue-violet light.

DOG COLLAR - A broad choker worn tightly around the neck, often set with parallel strands of gemstones or pearls.

DOUBLE REFRACTION - Light entering a gemstone where the beam is split into two rays.

DOUBLET - An assembled stone with two pieces fused or cemented together. 
Sometimes an opal with a quartz cap or a garnet top with a glass pavilion. Easily detected using immersion.

DOUBLING - Facet edges, scratches or inclusions that are doubled when viewed in a doubly refractive gemstone.

DR - Double refraction or doubly refractive. Light entering a gemstone where the beam is split into two rays.

DURABILITY - The combination of hardness, toughness and stability that describes the ability of a gemstone to resist breakage and wear.

DWT - The abbreviation for pennyweight which is equal to 1/20th of a troy ounce or approximately 1.555 grams.  

E:

ELECTROPLATING - A process where an electric current deposits a layer of metal from a plating solution on a piece of jewelry.
 Rhodium plating is an electroplating process.

EMERALD FILTER - Also known as a Chelsea Filter, imitation gems appear green while natural and synthetic emerald
 (and some other natural gems) have a reddish color.

ENAMEL - In jewelry, a vitreous glaze that is usually fused glass heated to a base, most commonly to the surface of metal.

ENGINE TURNING - A process to decorate a metal surface by moving the surface of the object against a rotating blade.

ENGINE TURNED EFFECT - Seen on ivory, a distinct grain of intersecting lines with a diamond shape between them.

ENGRAVING - A technique where metal is cut away with a graver to form a design or lettering.
 Once commonly done by hand but mostly done by machine today.

ETCHING - The process of using acid to remove or alter a metal surface for a decorative effect.

F:

FACET - A flat polished surface of a gemstone that increases brilliancy and beauty when cut at the proper angle. 

FACETED GIRDLE - A girdle of a diamond that has many flat facets around the circumference of the stone.

FACETING - The act of cutting a gemstone, generally transparent, to increase its brilliancy and beauty.

FEATHER - A cleavage, fracture or break in a gemstone, typically healed, that often has a white and feathery in appearance.

FILIGREE - Fine gold or silver wire twisted to form an openwork pattern and soldered into place. 
Reaching its peak during the Edwardian period, most filigree is stamped today.

FINDINGS - Pre-manufactured gold and silver parts of jewelry such as heads, settings, clasps, jump rings, earwires and pins.

FINISH - The term that refers to the quality of the gemstones polish and symmetry.

FIRE - Another name for dispersion which shows the flashes of spectral colors seen in gemstones.

FLAW - An imperfection visible at 10x magnification.

FLORENTINE FINISH - A finish, done by hand and put on with a line graver. 
First, one set of lines is put on and then a perpendicular set of lines is laid on top of the first.
 A deep finish that takes more time but lasts much longer than a satin finish.

FLUORESCENCE - The visible glow from a gemstone when it is subjected to ultraviolet light. 
Diamonds, under ultraviolet light, will often emit a visible light of  blue or yellow.

FLUX - A solution used in soldering to keep the metal from oxidizing which would impede the flow of solder.

FOB - A chain that secures a pocket watch to a man's vest, or any ornament that hangs from such a chain.
 An adornment that hangs from a watch chain.

FOILING - A technique used to enhance the color of a gemstone or imitation, 
by inserting a colored or silver foil behind it, in a closed-end setting. Used most often in the production of rhinestones.

FOUR C'S - Four terms,  all starting with the letter "C," describing a diamond's value characteristics. Cut, color, clarity, and carat weight.

FOUR-PHASE INCLUSION - Very rare. A host crystal containing a negative crystal filled with gas, a liquid and a crystal inclusion.

FRACTURE - A break within a gemstone, often around the girdle.

FRACTURE FILLING - A treatment applied mostly to diamonds.
 Fissures on the surface are filled with a substance having an RI similar to that of diamond 
so that it blends with the gem to improve clarity. Also used in emeralds.
 The process in diamond is fairly stable unless the stone is exposed to high heat such as that from a jeweler's torch.

FRESHWATER PEARL - A cultured pearl formed in a freshwater mollusk. 
Mantle tissue from a mussel is inserted into mussels living in freshwater lakes or rivers. 
 Freshwater pearls are less expensive than salt water cultured pearls. 

FULL CUT DIAMOND - A description of a round  brilliant cut stone with 57 to 58 facets,
at least 32 above the girdle and 24 below the girdle. The term also may apply to colored gems.

G:

GALLERY - Strips of metal, with a pattern resembling the gallery of an early sailing ship, on the sides of a ring.
 A type of mounting with a pierced, openwork design, usually in support of heads for stones.

GERMAN SILVER - An alloy of copper, zinc and nickel. A misnomer, there is no silver in German silver.

GIRANDOLE - A style of earring or brooch in which a large stone or decorative motif, such as a bow, 
suspends three smaller pear-shaped stones or pearls.

GIRASOL - An opal with flaming red, orange and yellow colors. The term is rarely used anymore.

GILDING - A process of covering an object, such as silver, base metal, wood, with a thin layer of gold, gold leaf or gold foil. 

GIRDLE - The narrow band around the widest part of a faceted gemstone. It separates the crown and the pavilion.

GEMSTONE - A mineral, combination of minerals or organic material that possesses rarity, durability,
 and beauty thereby creating desirability.

GEMSTONE ENHANCEMENT - The human process by which the appearance of a gem is improved. 
Heat enhancement, an excellent example, is most often used to clarify a gem or improve its color.

GEODE - A rock, often spherical, having a hollow lined with crystals, often amethyst or peridot.

GOLD - A shiny, bright-yellow, precious metal mined from the earth. Too soft in its native state
 it is commonly alloyed to make it stronger and lessen the cost.
 In the 24 part karat system, gold is typically 14 parts gold and 10 parts alloy 
(stamped 14K or 585) or 18 parts gold and 6 parts alloy (stamped 18K or 750).

GOLD PLATE - A base metal that is electroplated with gold. Also known as gold flash, gold finish, gold tone or gold dipped.

GOLD FILLED - A layer of gold bonded to a base metal.
 The weight of gold must be 1/20th of the total weight or more and must be 10KT or better.
 Wears better than a gold plated item because there is much more gold.

GRAIN - A unit of weight equal to 0.25 of a carat.

GRAM - A metric unit of weight equaling 5 carats. There are 28.35 grams in an avoirdupois ounce. 
Often used in expressing the weight of precious metals such as gold and silver.

GRANULATION - The process of decorating a metal surface with tiny grains of metal

GRAVER - A tool similar to a chisel used for engraving metal or raising beads in the stone setting process.

GREEN GOLD - Gold with a high proportion of silver.

GREY GOLD - Gold with a high proportion of iron.

GUEST CRYSTALS - A gemstone inclusion inside the host crystal. Essentially an included crystal.

GUILLOCHÉ Enamel - A type of enamel work in which the metal is turned on an engine lathe 
to form a pattern and then enameled over the pattern.
 Was used for decorating valuable objects such as Fabergé eggs and pocket watches.

GYPSY SETTING - A setting in which the stone is set low into the surrounding metal 
with the table of the stone almost level with the top of the metal surface.

H:  

HALLMARK - A mark stamped on gold, silver or platinum by an assay office after
 the metal has been tested and shown to contain the proper amount of precious metal as required by law.
 Purity determined after assaying.

HANDMADE - The FTC defines handmade as entire shaping and forming of a product 
from raw materials and accomplishing the finishing and decoration 
by hand labor and manually-controlled methods which permit 
the maker to control and vary the construction, shape, design, and finish of each part of the product.

HEAT TREATMENT - The application of heat to a gem for the purpose of improving its color or clarity. 
Many gems are treated in this manner, including rubies and sapphires.

HABIT - The crystal form in which a mineral most often occurs.
 The most common habit of diamond is the octahedron, but it comes in other habits such as the macle or the cube.

HARDNESS - The ability of a material to resist scratching. A gemstone which is the same hardness as another, or softer, will be scratched.

HEXAGONAL - One of the seven crystal systems in gemology.
 Has three equal axes at 60 degrees and a fourth axis perpendicular 
to the other three and unequal in length.
 Some hexagonal gems include quartz, corundum, beryl, tourmaline and calcite.

HUE - The primary color, such as red, blue or green.

I:

ILLUSION SETTING - A setting that gives the impression of a larger diamond
 by use of a highly polished white gold reflecting plate around the stone.

INGOT - A bar or brick of precious metal.

INLAY - A piece containing gems, woods and metals which are cemented together and ground down to create a smooth surface.

INVISIBLE SETTING - A channel setting using stones that are scored on the pavilion 
and snap into place on wire lattice under the stones.
No metal shows from the top giving the piece the "invisible" look.

IMPERFECTION - Any surface blemish, internal flaw or inclusion in a gem.

INCLUSIONS - Internal characteristics present in gemstones other than fracture or cleavage.
Common diamond inclusions are feathers, crystals, internal graining and pinpoints.
Often displays different colors from the rest of the stone. 
In colored stones inclusions may be solid included crystals or negative voids.

INORGANIC - Any substance that does not come from living organisms.

INTERFERENCE - The effect of two or more light waves moving along the same path after traveling different distances. 
When they are "in phase" they reinforce each other which intensifies the color. 
They will cancel each other out if they are "out of phase.
" Play-of-color in opal occurs when the interference of white light results 
in the cancellation of some wavelengths and reinforcement of others.

INTERFERENCE FIGURE SPHERE - A small sphere used to determine uniaxial and biaxial figures in doubly refractive gems.

INTAGLIO - A gem, or shell, engraved or carved into the object so that it sits below the surface level of the material.
An intaglio is the opposite of a cameo.

IRIDESCENCE - Rainbow colors inside or on the surface of a material caused 
by inclusions interfering with light entering the stone. Fire agate is an excellent example of iridescence.

ISOMETRIC - The crystal system with the greatest symmetry. Has three equal cyrstallographic axes, all at right angles. 
Also known as the cubic crystal system. Some of the most important gems from this system are diamond, garnet and spinel.

J:

JABOT PIN - Designed to hold the jabot (a kind of ruffle) onto the shirt. 
It is a pin with a brooch at either end one of which is removable so that the pin 
can be stuck through the garment and then secured by reattaching the removable brooch. 
A form of Art Deco mourning jewelry. 

L:

LABRADORESCENCE - A flash of color caused by the interference of light due to repeated twinning.
 Primarily on the surface. Most commonly seen in labradorite.

LACE BROOCH - A small brooch, usually set with diamonds, worn in the later 19th century.

LAPIDARY - An artisan or craftsperson who cuts, facets, carves, engraves and polishes gemstones.

LAVALIERE - A chain from which an ornament or gemstone hangs in the center.

LIQUID INCLUSION - A negative crystal inclusion or space within a gem that is filled or partially filled with a liquid.

LOCKET - A hinged pendant, often engraved on the outside, which opens to areas where small photos can be kept.

LOST WAX CASTING - The method of casting metal that uses a wax pattern
 from which an investment mold is made. The investment is heated and the wax melts away (or is "lost") 
and the metal is poured or injected  into the form where the wax once was.

LOUPE - A small magnifying glass used by jewelers and gemologists to examine stones.
 10X (ten power or ten times normal) is the standard magnification for diamond and colored stone grading.

LOWER GIRDLE FACETS - The 16 pavilion facets (8 matching pairs), 
extending from the girdle, in between the pavilion main facets.

LUSTER - The quality and quantity of reflected and refracted light from the surface of a gemstone or pearl.

M:

MABÉ - Mabé means "half," and this term is used to denote the large half pearl, flat on one side, 
that forms inside a mollusk. Also known as blister pearls.

MACLE - A flat, often triangular, diamond that is a twinned crystal. Most macle rough is cut into fancy shapes.

MAKE - A trade term which refers to the proportions, symmetry, and polish of a gemstone.

MATINEE LENGTH - A strand of pearls 20" - 24" in length.

MELANGE LOT - A parcel of stones in the same size range with a mix of color, clarity, and cut grades.

MELEE - A term used primarily to describe small, round faceted diamonds or colored stones of less than .20 carats (1/5th of a carat).

METAMICT - The condition of a mineral which occurs with the breakdown of its crystal structure due to radioactivity.
 Zircon is rendered into a nearly amorphous state as the radioactivity of uranium or thorium slowly destroys the crystal lattice.

MILGRAIN - A raised, beaded edge on a ring either done with a special engraver's tool or cast into the piece.
 Often seen on wedding bands.

“MISSISSIPPI” RIVER PEARLS - Irregularly shaped, elongated freshwater pearls.

MINERAL - An inorganic, natural material that usually possesses a crystal structure and has a characteristic composition.

MOH'S SCALE - An arbitrary scale of hardness devised by Friedrich Mohs, 
a German mineralogist, in the 19th century. Assigned with numbers from 1 to 10 (with 10 being the hardest).
Note that diamond is many times harder than corundum. The comparative scale of hardness is as follows:

1) talc

2) gypsum

3) calcite

4) fluorite

5) apatite

6) moonstone

7) quartz

8) topaz and beryl

9) corundum

10) diamond

MONOCHROMATIC - Possesses a single color.

MONOCLINIC - One of the seven crystal systems in gemology.
Has low symmetry and all the axes are different lengths. 
Two of them, the A and C axes, meet at 90o, but the third does not.

MOTHER-OF-PEARL - The substance lining the inside of a mollusk.
Used for many things including buttons, "pearl" handles on hand guns and as inlays on many objects.

MOUNTING - A term for the part of jewelry in which a gem or other decorative object is set.

N:

NACRE - The iridescent substance secreted by a mollusk that forms the outer surface of a pearl.

NATURAL - The term for a piece of the original skin of the diamond that is left as the stone is being shaped.
Naturals can be found on the culet (usually on Old European or Old Mine cuts) or on any indented area
of the stone, but are usually found near the girdle. They are represented in green on a plotting diagram.

NATURAL PEARL - A pearl that originates naturally in a mollusk without the aid of human help.

NEGATIVE CRYSTAL INCLUSION - A void in a host crystal that takes on the habit of the host crystal. 
An empty cavity is known as a single-phase inclusion. 
If the cavity contains a gas or a liquid it is a two-phase inclusion. 
If the cavity contains a gas or liquid and a crystal it is called a three-phase inclusion. 
The very rare four-phase inclusion would be composed of the negative crystal filled with gas, a liquid and a crystal inclusion.

NICK - A very small chip on the surface of a diamond.

  

O:

OFF ROUND - A pearl that has a slightly irregular shape, not "round."

OIL TREATMENT - A treatment using oil, often used on emeralds and rubies 
to keep inclusions from detracting from the beauty of the stone. 
Should be disclosed to the consumer at the time of purchase.

OPALESCENCE - A variety of adularescence, it refers to cloudiness inside a stone, not actual play-of-color.

OPAQUE - A gemstone that allows no transmission of light, not even thin pieces.

OPERA LENGTH - A strand of pearls 28" to 30" in length.

ORIENT - The iridescent phenomenon on or just below the surface of a pearl.
Caused by the interference and diffraction of light from the minute aragonite
and calcite crystals comprising the pearl's nacre.

ORGANIC - Any gem, such as jet or amber, formed by a living organism.

ORTHORHOMBIC - In this system there are three axes, all of which meet at 90o to each other. 
However, all the axes are a different length. Orthorhombic gems include peridot and topaz.

P:

PALLADIUM - A white metal belonging to the platinum group, it weighs a little more 
than half as much as platinum and sells for slightly more than half the price. 
Palladium is sometimes alloyed with gold to obtain a greenish tint.

PARURE - A suite of matching jewelry with at least three pieces,
usually containing a necklace, earrings, brooch and a bracelet.
Sometimes also a belt.

PASTE - A high content leaded glass imitation of a gemstone. 
May be backed with colored foils to imitate other gemstones (similar to rhinestones).

PATINA - Discoloration that forms on an object's surface resulting from natural aging due to wear and oxidation. 
Often planned for in the artist's design, patina can be introduced artificially by use of chemicals. 
Antique jewelry is expected to have patina and if it is cleaned or polished off, the value of the piece may be less.

PAVÉ - To be classified as pavé, a setting must have one prong touching three or more stones.
Otherwise, it is a cluster. The pavé setting is most often used with diamonds.

PAVILION - The area of a faceted gem that lies below the girdle. The bottom of the stone.

PAVILION MAIN FACET - The elongated kite shaped facet on the pavilion of a brilliant cut stone. 
There are eight pavilion main facets on the standard round brilliant cut.

PEARL ESSENCE - A coating, made from the scales of a herring, that adds a pearl-like luster to simulated pearls.

PENDALOQUE - A brooch with a tear drop or pear shaped gemstone suspended
 from a smaller stone which is separated by a bow or other motif.

PENNYWEIGHT - A unit of weight for precious metals. 1/20th of a troy ounce.

PERFECT - The Federal Trade Commission states "It is unfair or deceptive to use the word "perfect," 
or any representation of similar meaning, to describe any diamond unless
 the diamond meets the definition of "flawless" and is not of inferior color or make.
" Jewelers should avoid its use entirely.

PHENOMENA - Properties that some gemstones exhibit. An excellent example of a phenomenon is the chatoyancy of chrysoberyl cat's-eye.

PIETRA DURA - A composition or mosaic of gemstones, such as agate, chalcedony, 
lapis lazuli or sardonyx set into a floral pattern. 
Was sometimes applied to the panels of furniture. Also known as a hardstone mosaic.

PIQUÉ- Tortoiseshell which is inlaid with mother-of-pearl, silver or gold. 
Produced by pressing a heated piece of gold or silver into the shell, which causes it to melt slightly. 
When the shell cools it hardens around the metal. Popular in the 18th and 19th centuries.

PLANISHING - A hammering or refining process done to give a smoother finish 
to the surface of a metal object with highly polished hammer faces.

PLATINUM - A dense, heavy, non-corrosive silver white metal, which resists erosion extremely well. 
The rarest of the three precious metals (platinum, gold, silver). Used in a nearly pure form from 85% to 95%.

PLAY-OF-COLOR - The fire of an opal. An array of moving colors flashing on and off as the opal 
or the light source moves. Caused by the orderly arrangement of tiny spheres inside the stone 
that interfere with the light waves hitting the stone. A result of diffraction.

PLEOCHROISM - Two colors (dichroism) or three colors (trichroism) created when the beam
 of light enters a doubly refractive material. The beam splits in two and they are absorbed unequally.

PLIQUE Á JOUR - An enameling technique in which the design is outlined in metal 
but has no metal backing and is filled with a transparent enamel. 
Creates a stained glass window effect. From the Art Nouveau era.

PLOTTING DIAGRAM - A diamond outline diagram included on diamond reports
 that illustrate the facets (printed in black) and the approximate location 
and type of internal and external characteristics (printed in red and green).

PLUMB GOLD -Gold that meets the stamped karat content. 
An assurance that gold is not under karated which was allowed before 1976.
 A stamp in a ring such as 14KP means the item is plumb (not plated), having the full 14 parts gold and 10 parts alloy.

POINT - A metric weight of a gemstone equal to 1/100 of a carat. 0.75 carats is equal to 75 points.

POLARISCOPE - A gem instrument that utilizes two polarizing filters, 
one of which rotates, to determine pleochroism, single and double refraction and to resolve interference figures.

POLARIZED LIGHT - Light waves uniformly aligned in a single plane.

POLISH - The final finish on the surface of a fashioned gem.
Optical reflection is maximized when the stone is polished as finely as possible.

POLISHED GIRDLE - A girdle that has been polished. Rarely done with diamonds.

PRECIOUS STONES - An obsolete term which refers to diamond, emerald, sapphire, or ruby. 
Should be avoided in the industry.

PRIMARY DEPOSIT - A deposit where the gem (or mineral) is found in its original rock.

PRINCESS LENGTH - A strand of pearls 18" in length.

PRONG - A prong is a tiny metal arm or claw that is part of the setting which holds a stone in place.

PROPORTIONS - Proportions and finish make up the "cut" of a diamond.
Proportions are the size and angle relationships between the facets and other parts of the stone.

R:

REFLECTION - The return of light to the eye from the surface of stone. 
Light is reflected at the same angle to the normal as the angle of incidence.

REFRACTION - The bending of light rays as they enter a gemstone at angles other than perpendicular to the normal.

REFRACTIVE INDEX - The ratio of the velocity of light between the air and the gemstone.
Developed by Willebrord Snell in the seventeenth century.

REFRACTOMETER - An instrument that measures the gems critical angle and translates it into a refractive index figure.

REPOUSSÉ - A method of embossing a metal object by hammering 
a design from the back of the metal to form a three-dimensional bas-relief surface.

RHINESTONE - Glass, higher quality crystal, or rock crystal which are faceted 
into diamond and gemstone imitations with a foil back to increase reflectivity.  

RHODIUM - A white metallic element of the platinum group. Widely used for electroplating white gold.

RIVIÉRE - A choker type necklace composed of a single strand of gemstones, usually diamonds, of the same size and cut.

RONDELLE - A pierced, flattened ball or saucer shape made of metal or a gemstone strung between the beads in a necklace.

ROSE CUT - An early type of diamond cut dating from the mid-seventeenth century.
The diamond is cut with 24 triangular, hexagonally arranged facets that terminate in a point. 
The bottom of the stone is flat.

ROSE GOLD - Gold that has been alloyed with copper and silver producing a pink tint.  
Tends to tarnish more quickly than other gold alloys.

ROUGH - Material that is uncut or unpolished into a gemstone. The raw, natural state in which gems are found.

  

S:

SATIN FINISH - A finish on gold, achieved by brushing the surface to create a silk like luster instead of a high polished surface. 

SAUTOIR - An extremely long neck chain, usually made of chains, beads, 
or pearls and ending in a tassel or fringe. Popularized in the Edwardian era because Queen Alexandra often wore them.

SCARAB - An engraved or carved gem used to represent a Mediterranean beetle. 
Considered to be a symbol of the soul by the ancient Egyptians.

SCHILLER - A glow caused by light reflecting off the inclusions of copper or hematite platelets. 
A form of aventurescence commonly found in sunstone.

SCINTILLATION - Sparkling reflections or flashes of light off of the facets 
of a diamond or gemstone when the light source or the observer moves.

SEED PEARL - A small pearl that measures approximately two millimeters or less.

SEMI-PRECIOUS STONES - An obsolete term used to describe gemstones of lower price
(not diamond, emerald, sapphire, or ruby). These terms are misleading and shouldn't be used in the trade.
Many so-called "semi-precious" gemstones are extremely valuable, and more rare than lower grade "precious stones." 

SHANK - The band of a ring that encircles the finger and to which the head or setting for stones or pearls is attached.

SILK - The term for long needle-like crystal inclusions. Found in corundum, garnets and other stones. 
Can cause phenomena such as cat's eyes and asterism.

SILVER - Pure silver is 0.999 or 99.9% pure, occurring naturally in the earth. 
Because it is too soft to be used in jewelry in this form it is alloyed with copper..

SIMULANT - Any substance or stone used to imitate the appearance of a natural gemstone.
 Natural stones such as colorless sapphire can be used to simulate diamond.

SINGLE CUT - A round cut with 17 or 18 facets: 8 bezel, 8 pavilions, a table and possibly a culet.

SINGLE-PHASE INCLUSION - Any solid included crystal or negative crystal in the host mineral.

SOLITAIRE - A term that refers to a ring containing a single gem, usually a diamond.

SPECTROSCOPE - An instrument for viewing gem spectra.
There are two basic types, the prism spectroscope and the less expensive diffraction-grating units.
The prism units allow more light to enter so absorption lines stand out more and have greater contrast. 
Diffraction spectroscopes spread the colors out more evenly so it is easier to see in the red and violet end of the spectrum.

SPECIFIC GRAVITY - The ratio of the weight (or density) of a material to an equal
volume of water at 4 degrees Centigrade.

SR - Singly Refractive or single refraction.

STAR FACETS - The eight triangular facets that surround the table of a round brilliant stone. 
The star facets meet the top of the kite shaped bezel facets.

STAINLESS STEEL - A durable metal typically used in creating watch cases, flatware and bands.
 Steel alloyed with nickel.

STERLING SILVER - A homogenous mixture of 92.5% fine silver and 7.5% copper.

SYMMETRY - The consistency of the shape, positioning and arrangement of the facets.

SYNTHETIC - Essentially the same physical, optical and chemical properties 
as a natural gemstone but it is man-made. Another term for synthetic is lab created.

T:

TABLE - The largest facet on the crown of a faceted gemstone.

TABLE PERCENTAGE - The comparison of the size of the largest table facet to the average width of the stone at the girdle.

TENEBRESCENCE - A mineral that changes color between light sources. 
The change can take a few seconds to several weeks to occur, making it different than the color change phenomena.

TENSION SETTING - Setting in which opposite ends of a setting hold a stone
 by pressure or the force of tension, making it appear as if it is floating.

TETRAGONAL - One of the seven main crystal systems used in gemology. 
Has three axes that all meet at 90o. It differs from the isometric system
because the C axis is longer than the A and B axes (which are the same length).

THREE-PHASE INCLUSIONS - A cavity in the host crystal which contains a gas or liquid and a crystal.

TITANIUM - A hypoallergenic, ultra-light and very strong gray metal.
Becoming more common in jewelry and used extensively in watches, it is resistant to salt water corrosion.

TONE - The lightness or darkness of the color of a gemstone. 
The tone scale ranges from 0 (colourless/white) to 10 (black).

TOUGHNESS - The ability of a gemstone to resist breaking.
Toughness is not the same as the hardness of a stone, which is a stones ability to resist scratching.

TRANSPARENT - The quality of the transmission of light through a gemstone which shows a minimum of distortion.

TRANSLUCENT - Diffusely transmitted light such as you would see through frosted glass.

TREATED GEMS - A catch-all term that describes gemstones that have been modified to improve their clarity or color. 
Processes include dyeing, heat, laser drilling, fracture filling (clarity enhancement), 
impregnation, smoking treatment, sugar treatment, high pressure high temperature (HPHT), annealing and irradiation. 
Some treatments require equipment that the average gemological lab won't have.

TRICLINIC - One of the seven crystal systems in gemology. 
All the axes are different lengths and none of them meet at 90 degrees. 
The least symmetrical of the crystal systems.

TRIGONAL - One of the seven crystal systems in gemology.

TRIGONS - Triangular shaped pits or indentations found on the octahedral faces of Diamonds.
Trigons are the result of the growth process.

TWINNING or TWINNED CRYSTALS - Two or more mineral crystals that have grown together
in a symmetrical nature, usually nonparallel.

TWO-PHASE INCLUSIONS - A void in a host crystal containing a gas or a liquid.

TROY OUNCE - A unit of weight for precious metals. Twenty pennyweights (dwt) equals one troy ounce, 
and twelve troy ounces equals one troy pound.

 

U:

ULTRASONIC CLEANER - A cleaning machine that vibrates thousands of times per second.
Fragile gems such as opal, emerald, pearls and many other should not be put into the ultrasonic.

ULTRAVIOLET LIGHT - Consisting of wavelengths shorter than those of visible light
 making them invisible to the naked eye. In gemology, the UV lamps are short-wave and long-wave (315-400 nanometers).

UNIAXIAL - Having only one optic axis in a doubly refractive gem. 
Only gems from the tetragonal or hexagonal crystal systems are uniaxial.

UPPER GIRDLE FACETS - The 16 facets on the crown (8 matching pairs) that meet the star facets and the girdle.

V:

VERMEIL - Gold plated silver.

W:

WHITE GOLD - An alloy of gold that has nickel as the main agent for creating the silvery color. 
Needs to be rhodium plated on a regular basis to maintain a bright white color or it will turn slightly yellowish. 
Not found in nature.

Y:

YELLOW GOLD - The natural color of pure gold is a deep yellow. 
As the alloys increase the color of the gold begins to pale. 
Therefore, 18K yellow gold has a deeper color than 14K or 10K yellow gold.

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                                                                             ... Written (2009/Info 1999/USA)….. By George K.Kiamos FGA, DGA  ...

                                     Minerals Symbols List (for Mineral Maps):