Hopefully the following glossary of diamond terms and phrases will help answer all those questions you have.
Abrasion – Small nicks found along the facet junctions which produce fuzzy lines rather then sharp facet edges.
AGS – Acronym of American Gem Society.
Baguette – Another term for a rectangular step cut diamond.
Bezel – A facet on the upper part of the diamond.
Blemish – All damage which occurs on the surface of a diamond as opposed to internal inclusions.
Bow Tie Effect – A shadow in some diamond shapes caused by light leaking out of the bottom of the diamond.
Brilliance – A combination of luster, light reflection, color dispertion and scintillation.
Brilliant Cut – A 57 facet round cut diamond. Designed for maximum brilliance and sparkle.
Bruise – Surface crumbling damage which is sometimes accompanied with tiny feathers.
Burn Mark – Clouding on the diamond surface caused by heat.
Carat – The unit of weight for a diamond. 1 carat = 200 milligrams.
Carbon Spots – Black colored inclusions caused by minerals such as graphite or hornblende.
Cavity – A deep opening in a diamond.
Chip – A small missing piece caused either by cutting or normal wear and tear.
Clarity – The presence of identifying characteristics on or within the stone.
Clarity Enhanced – A diamond with an improved appearance by filling fissures or fractures with a clear substance.
Cleavage – The tendancy of a mineral to break in certain fixed directions.
Clouds – Minute inclusions which are indistiguishable from one another and appear as a milky cloud in the diamond.
Color – The color of the diamond on a scale from D to Z.
Crown – The part of a faceted diamond which is above the girdle, comprising the table and other facets.
Crown Angle – The angle between the bezel facets and the girdle plane.
Crystal Inclusions – Other minerals included within the diamond.
Culet – The small facet polished across the sharp point of the pavillion of a faceted stone.
Cut – Also called make, it refers to the proportions and finish of a polished diamond.
Dark Crystal Inclusion – Can also be called grain. They are inclusions of crystals which appear dark rather than white or transparent under a microscope.
Depth – The distance from the culet and the bottom to the table facet at the top. It is always measured in millimeters.
Depth Percentage (%) – The percentage of the diamond depth to its width.
Diameter – The width of a diamond measured between two opposing points along the girdle’s outline.
Diamond – A diamond is a metastable allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice.
Diamond Cutting – The process of changing a diamond from a rough stone to a faceted gem.
Diamond Gauge – A tool used to measure diamonds and other precious stone. Usually has several arms in the style of a ‘Swiss army knife’.
Dispersion – The light reflecting off the facets due to angles cut into the diamond. Can also be referred to as the display of spectral colors.
Emerald Cut – A rectangular diamond shape with cut corners.
Eye Clean – A diamond which has no visible inclusions to the naked eye. Normally refers to a grade of around SI-1 or higher.
Face Up – A diamond help the correct way up.
Facets – The small surfaces polished onto a rough diamond which give the diamond its shape.
Faceted Girdle – The polishing of a girdle into small facets.
Fancy Color Diamond – Any diamond with a nice color other than light yellow.
Fancy Shapes – Any diamond cut into a shape different than the brilliant round. Examples are Asscher, Heart, Pear etc.
Feathers – An inclusion or break in the diamond which often appears white or feathery.
Finish – Describes the polish and symmetry of the finished diamond.
Fire – A term which can be used interchangeably with brilliance or dispersion to describe the variety and intensity of colors when light is reflected from within the diamond.
Flaw – A diamond’s imperfection.
Fluorescence – The bluish glow of some diamonds seen under ultraviolet light, from none to strong.
Fracture – A crack in a diamond.
Full Cut Diamond – A brilliant cut round diamond with either 57 or 58 facets.
Girdle – The narrow band around the widest part of a cut diamond, which divides the crown and pavillion facets.
Heart-Shape Cut – A diamond cut into a heart shape.
Included Crystal – A crystal contained within a diamond.
Inclusion – Imperfections found within a diamond. May be either visible to the naked eye or under magnification.
Internal Graining – Internal irregular crystal growth, which may appear as either milky areas or faint lines or streaks.
Laser Drill Holes – Used to drill into a diamond so a black inclusion can be boiled away using acid.
Length to Width Ratio – The ratio of a cut diamond’s length to width in elongated diamond shapes such as marquise.
Loupe – A magnifying glass with a 10x magnification which is used to examine diamonds.
Make – See ‘cut’.
Marquise Cut – A fancy shape diamond which is elongated with points at either end.
Melee – Small, round faceted diamonds of .18 carats or less.
Mounting – The part of a piece of jewelery in which a diamond is set.
Naturals – Small parts of a rough diamond which are sometimes left near the girdle by a cutter when polishing a diamond.
Needle – A long thin inclusion which looks like a tiny pin or needle.
Nick – A small chip on the diamond surface, which is normally found near the girdle.
Oval Cut – A particular type of fancy cut diamond which is oval in shape.
Pavé – A term used for lots of small diamonds being used as a diamond overlay on the metal of a piece of jewelery.
Pavilion – The bottom part of a diamond, under the girdle.
Pear Cut – A type of fancy shape diamond which looks somewhat like a teardrop.
Pinpoints – Miniscule internal spots in a diamond.
Pit – Tiny opening in a diamond.
Point – The weight of a diamond equal to one hundredth of a carat.
Polish Mark – Cloudy surface marks caused by excessive heat.
Polished Girdle – A girdle which has been polished to a highly reflective surface.
Princess Cut – A fancy cut diamond shape which can be either square or rectangular.
Proportions – The relationship between the angles of the facets of a cut and polished diamond.
Radiant Cut – A fancy cut diamond shape, which resembles a square or rectangle without corners.
Refraction – The change in direction of light as it hits a diamond plane.
Rough – A raw diamond before it’s cut and polished.
Scintillation – Also called sparkle. Refers to the combination of fire and brilliance, which is the amount of light which reflects out of a diamond.
Single Cut – A brilliant cut diamond with either 17 or 18 facets.
Sparkle – See ‘scintillation’.
Symmetry – Grade given to the arrangement of facets and finished angles after a diamond has been cut and polished.
Table – The horizontal top facet on a diamond.
Table Percentage (%) – The percentage of the width of the table divided by the total diameter of the diamond.
Treated – Diamonds which have been modified to improve their color or clarity.
Trillion Cut – A triangular fancy cut diamond shape.