Diamond Glossary

Unlike in our previous entry on basic terminology, in this glossary, we will focus on terms, some basic, others more advanced, but all used by people within the industry to some extent, and CEDEX thinks you should know.


Just like our basic terminology – this page too will sometimes be updated with more terms, so if you would like to suggest a few you feel are missing – let us know!


BOURSE: A meeting place (Trading Floor) where diamond dealers meet for business transactions.


BLEMISH: An imperfection on a diamond’s surface that may or may not be recognizable.


BLING: This term is used to refer to an individual who adorns over-the-top jewellery, with the purpose of showing off their wealth.


BRILLIANCE: The intensity of the reflections (fire) coming from the diamond.


CARAT (CT.): Unit of metric measurement used for diamonds; one carat equals .2 grams, or .007 ounces


CLOUD: A minor inclusion within a diamond.


CONFLICT DIAMONDS: Mined rough diamonds used to fund rebel and revolutionary activities against legitimate and internationally recognised governments.


CRYSTAL: An inclusion within a diamond that looks like a bubble.


DEAD: A diamond showing no lustre or brilliance as a result of heavy inclusions.


DIAMANTAIRES: The French term ‘diamantaire’ used in the diamond industry to denote a person who possesses diamond-related expert skills.


DOWNSTREAM: The stage in the diamond value chain that includes the retailing of jewelry to end-consumers.


EYE-CLEAN: A diamond with no visible inclusions or imperfections, when viewed with the naked eye.


FACET: The plane surfaces of a diamond created by diamond polishing.


FANCY COLOUR: The colour of the diamond, other than white (D to Z on the colour grading scale).


FEATHER: An internal inclusion that looks like a small white feather.


FIRE: Light that enters a diamond and is then returned to the viewer


FLUORESCENCE: The light emitted by a diamond when exposed to ultraviolet light.

FLAW: An inclusion, such as a blemish, fracture or cavity.


FLAWLESS: A diamond with no inclusions.


GIA: Gemological Institute of America: A US-based non-profit organisation established in 1931 that engages in research, gem identification and grading services


GEM-GRADE: A rough or manufactured precious stone, fine enough for use in jewellery.


GLETZ: A crack, sometimes called a feather.


GRAIN: 1/4 of a carat; 1ct = 4 grains


INCLUSION: An internal characteristic found in a diamond


IRRADIATED DIAMOND: A diamond exposed to radiation to alter its colour to a fancy colour.


KAPS: Pieces cleaved or lasered from a larger stone.


LUSTER: The quality of shining by reflecting light from the surface of a diamond.


LOUPE: Magnifying glass used in the diamond industry.


MASTER STONE: A diamond of a predetermined colour that is used for comparison in diamond markets and laboratories around the world.


OPAQUE: Refers to the transparency of a diamond. Generally, opaque material does not transmit light.


POINT: One one-hundredth of a carat. (1/100th)


SCINTILLATION: Reflections from the facets of a diamond seen as the stone is turned in the light


SIEVE: A tool for sorting rough or polished diamonds by size. Diamond sieve sets have interchangeable sieve plates each drilled with different sizes holes.


SORTING: The process of classifying rough diamonds into a variety of categories based on their natural characteristics, specifically their colour, clarity, carat and shape.


SYNTHETIC: A man-made diamond with the same chemical composition, crystal structure and physical properties as its natural counterpart.


TRANSPARENT, TRANSPARENCY: Ideally, a diamond should be completely transparent; any opacity is undesirable.


VALUE: Retail value versus wholesale value. (Analogy – you drive a car out of the showroom and it immediately loses a percentage of its value)


VS – VERY SLIGHTLY INCLUDED: VS stones have imperfections that are not easily seen. Small clouds and feathers are typical.


VVS – VERY VERY SLIGHTLY INCLUDED: VVS stones have slight imperfections that are difficult to see. Imperfections would be only visible from the pavilion or are small enough to be removed by re-polishing.


VIVID: The term vivid is used for colour grading of fancy coloured diamonds, to denote the most intensely coloured stones.


WINDOWING: Very small facets polished on to the rough diamond to see more clearly into the stone.