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 diamonds 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 cabochon 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.
Cabochon – 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 occurring along the crystal’s growth planes).
Cleavage Plane – Plane parallel 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.
Crystal inclusion – A crystal in a gemstone. Common in certain species of colored gems
Culet – Point or small facet at the convergence 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 light observed 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 pre forming, 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 observed through the crown.
Fish eye – 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; four of 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 irregularities 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 arrows in 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 blue ground).
Laser Cut – Fashioning a gem’s eventual shape using a laser
Laser Inscription – Laser engraved identifying 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 parallel marks 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 un faceted 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.
CSI – Clarity grade meaning slightly included: SI1 and SI2.
Simulants – Natural or synthetic substances meant to resemble a genuine gemstone.
Star Facet – Triangular 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 face tat 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 fluorescence in gemstones.
VS – Gem clarity grade meaning Very Slight; VS1 & VS2.
VVS – Gem clarity grade meaning Very Very 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 color grade.
Yield – Carat weight remaining after polishing – often expressed as a % of rough weight.