Common Terms Used With Gems

Abrasion - Damage to a facet edge, culet or keel line.

Adamantine - Quality of luster - like that of a diamond.

AGS - American Gem Society, Las Vegas, USA

Baguette - Rectangular narrow gem cut.
   Tapered - Gemstone cut in a trapezoid shape, one end narrower

Beard - Featherlike inclusion located on the girdle of a diamons and usually a result of improper bruting.

Bezel - Angled surface on a gemstone's crown - between girdle and table.

Bow Tie - Term used to describe a dark area seen through across the table of a diamond.

Briolette - Pear shaped faceted gemstone

Brilliance/Luster - Intensity of the light reflecting from a gem, observed through the crown.

Brilliant Cut - Collective name for diamond cuts where lower facets radiate from the center of the gem towards the girdle - round cut is most common.

Bruise - Crumbled area on a cut gem's surface, caused by a blow.

Buff Cut/Cab Top - A cut combining the features of a cabachon top with a faceted pavilion. Popular in men's jewelry. Minimizes facet junction abrasion.

Bruting - A process of shaping the girdle of a rough diamond.

Burn Mark - Mar on a gemstone facet surface due to overheating during polishing.

Cabachon - A gemstone fashioned with a domed or convex smooth and polished surface.

Cape (Color) - A term used to describe yellow diamonds found in the M to Z range of the color grading scale.

Carat - Standard unit of weight for gemstones - 1 carat = .2 gm

Cavity/Pit - An opening or indentation on the surface of a gemstone).

Certificate - Document provided by accredited laboratory defining a gemstones type, weight, color, clarity, proportions, finish grade, treatments. etc.

Chaton - A generally spherical stone that is faceted.

Clarity - Relative freedom from inclusions and imperfections of a gemstone. Usually expressed in a fixed grading scale for diamonds.

Cleavage / Feather - Break or fracture in the stone, internal or external and usually occuring along the crystal's growth planes).

Cleavage Plane - Plane parrallel to a crystal face.

Cloud - Milky area in a gemstone; made up of a multitude of very small inclusions.

Color Diamonds - Range from white to brown of a diamond and usually defined by standard nomenclature. Generally ranges from D - M.

Color Change - Ability of a gemstone to change hue/color when viewed under different types (wavelengths) of light. e.g. Alexandrite, color change sapphire.

 Colored Gems - The dominant hue of a gem. Identified by position on color wheel or by wavelength.

Crown - Portion of gem stone above the girdle.

Crystall incllusion - A crystal in a gemstone. Common in certain species of colored gems

Culet - Point or small facet at the convergance of pavilion facets.

Cushion - Square or rectangular cut with rounded corners. Numerous variations.

Cut - Proportions, make and finish of a polished gemstone.

D - Best color grade for diamonds. Very white.

Dead stone - A gemstone so heavily included that no brilliance can be observed.

Dispersion - Intensity of lightobserved through the crown of a gemstone.

Emerald Cut - Rectangular or square step cut with diagonal corners.

External characteristics - Imperfection on a gemstone's surface.

Facet - Flat polished surface on a finished stone.

Faceting - Process of creating facets on a gemstone.

Fancy color - Naturally colored diamonds with varying degrees of rarity.

Fancy Shape - Any shape other than a brilliant cut.

Fashioning - Process of manufacturing, i.e. designing, cleaving, sawing, bruting preforming, cutting and polishing.

Feather - Break or fracture in a stone, internal or external.

Finish - Quality of a gemstone's polish.

Fire/Brilliance/Internal Luster - Intensity and quality of light reflecting from a gemstone and observeed through the crown.

Fisheye - Usually diamonds where pavilion is too shallow. Result is a circular reflection of the girdle that can be seen through the table.

Fluorescence - Visible light occasionally emitted from diamonds during exposure to ultraviolet light.

C's - Carat, Cut, color & Clarity; fourof the factors used in determining the value of a gemstone.

Gem / Gemstone - Mineral or organic material with sufficient beauty, rarity and durability to be set into jewelry.

GIA - Gemological Institute of America,Carlsbad,USA

Girdle - Edge located between a gemstone's pavilion and crown.

Girdling - Process of shaping the rough stone's girdle.

Grain - Weight unit equivalent to 0.25 carats.

Graining - Natural iIrregularities seen internally or externally in the crystal structure of a gemstone. Often mistaken for polishing lines.

Hardness - A gem material's resistance to wear/ scratching measured on Mohs hardness scale.

Heart Shape - Modified brilliant cut with heart-shaped girdle, usually 56 facets. Cut is often to remove inclusions in an otherwise cleaner gem.

Hearts & Arrows - A gem cut to ideal proportions &l symmetry. Shows eight hearts shapes in a pavilion view and eight arrowsin a crown view, but only when observed through special viewers.

HRD - Hoge Raad voor Diamant (Diamond High Council), Antwerp, Belgium

IDC - International Diamond Council, Amsterdam, The Netherlands

IGI - International Gemmological Institute, Antwerp, Belgium

Imperfection - Blemish in a stone which occasionally reaches the exterior.

Included - One clarity grade which refers to eye-visible inclusions. I1,I2,I3.

Inclusion - Internal characteristic.

Industrial diamonds - Non gem quality diamonds.

Internal characteristics - Imperfection located within the stone.

Internal reflection - Light reflected off an internal surface of a gemstone.

Kimberlite - Volcanic diamond-bearing rock (also called blueground).

Laser Cut - Fashioning a gem's eventual shape using a laser

Laser Inscription - Laser engraved identifiyng text or numerals, usually on the girdle.

Laser Sawing - Laser division of a crystal.

Leveridge Gauge - Tool used to measure dimensions of a mounted or unmounted gemstone.

Lively stone - A stone with good brilliance and luster.

Loupe - Small magnifier used to examine gems. Usually 10X.

Loupe Clean - No inclusions seen under 10X magnification.

Make - Quality of symmetry and finish of a polished gem.

Marquise - Symmetrical boat shaped brilliant cut gem with pointed ends.

Masterstones / color samples - A set of polished gems which have been color graded by an accredited laboratory. Used to color-grade diamonds.

Mohs - Scale used to determine the hardness of minerals.

Natural - An original surface on a rough gemstone that is left untouched on the polished stone. Usually found on girdle.

Nick - Small chip on a gem surface or facet junction usually as result of contact with other stones.

Oval - Modified brilliant cut with an obround shaped girdle outline.

Parcel Paper - Folded papers used to hold polished or rough diamonds.

Pavilion - Part of a gem below the girdle.

Pavilion facet - Polished surface on the pavilion of a gem.

Pear Shape/Teardrop - Asymmetrical cut with one pointed and one rounded end.

Percussion Mark - crumbled area on the surface of a fashioned gem and normally resulting from a blow - usually white.

Pinpoint inclusion - Very small inclusion of any color indistinguishable as a crystal.

Pit/Cavity - Small opening on the surface of a polished stone.

Point - Weight unit, .01 (1/100) carat.

Pointer - Term used in describing polished stones under 1 carat.

Polishing lines - Small parallelmarks left on facets during the polishing process.

Polishing wheel - Flat cast iron wheel upon which gems are polished.

Princess - Modified brilliant cut with a square or rectangular girdle outline featuring 57 facets.

Proportions - Relative symmetry of angles and measurements on a polished gem.

Quality - Term used to descibe the overall color, clarity and cut attributes of a stone.

Radiant - Rectangular gemstone cut, often 70 facets, combining the shape of an emerald cut and sparkle of a brilliant.

Reflection - Return of light to the eye after striking an external or internal surface of a facet.

Rose Cut - Cutting style that produces a flat unfaceted base and a dome-shaped top covered with a variable number of triangular facets and terminates at a point.

Rough - Gem at found in nature before undergoing any manufacturing process.

Round Cut - Round brilliant cut.

Sawing - Process during which a rough gem is cut.

Scratch - Damage to a polished facet, usually appearing as a faint white irregular line. Often due to contact with other gems.

SI - Clarity grademeaning slightly included: SI1 and SI2.

Simulants - Natural or synthetic substances meant to resemble a genuine gemstone.

Star Facet - Tiangular facet on the crown of a brilliant cut next to the table.

Symmetry - The accuracy with which a gem is fashioned to a mirror image.

Synthetic - Non-natural, laboratory produced.

Table - Large facetat the center of the crown.

Thermal Conductivity - Ability of a material to conduct heat.

Trillion - Cut triangular shaped often 44 facets.

Ultraviolet - (Above Violet) Upper end of the light spectrum and invisible to the human eye. Shows fluorescencein gemstones.

VS - Gem clarity grade meaning Very Slight; VS1 & VS2.

VVS - Gem clarity grade meaning VeryVery Slight; VVS1 & VVS2.

Wavy Girdle - Girdle in a gemstone which has been improperly fashioned and does not run evenly.

Weight - Gem weight measure - carats, subdivided in grains and points.

White - A term to describe colorless gems and diamonds D- H colorgrade.

Yield - Carat weight remainding after polishing - often expressed as a % of rough weight.