Diamond Glossary
Key terms and definitions from the world of diamonds
Annealing
Heat treatment applied after irradiation to stabilise or further modify a diamond’s colour.
Learn moreAsscher Cut
A square step cut with cropped corners, known for its distinctive hall-of-mirrors optical effect.
Learn moreBaguette
A rectangular step cut, often used as an accent stone.
Bezel Setting
A setting where a metal rim surrounds the entire perimeter of the stone.
Brilliance
White light reflected from the upper facets of a diamond back to the observer.
Learn moreCape Diamond
A diamond with a yellowish tint caused by nitrogen impurities (N3 centre at 415.5 nm).
Learn moreCathedral Setting
A raised setting with arched shoulders resembling a cathedral.
Clarity Characteristics
Internal and external features (inclusions and blemishes) used to determine a diamond’s clarity grade.
Learn moreCoating
A surface treatment that applies a thin layer to alter a diamond’s apparent colour; not permanent.
Learn moreCrown
The upper portion of a diamond above the girdle — contains the table and crown facets.
Learn moreCrown Angle
The angle between the bezel (crown main) facets and the girdle plane, influencing the balance of fire and brilliance.
Learn moreDepth Percentage
The total height of a diamond divided by its average girdle diameter, expressed as a percentage.
Learn moreDiamond Grading Report
A document issued by a gemological laboratory detailing a diamond’s 4Cs, measurements, and identifying characteristics.
Learn moreFancy Vivid
The highest colour saturation grade for fancy coloured diamonds, indicating the most intense and pure colour.
Learn moreFluorescence Grades
The five-point scale used to describe fluorescence intensity: None, Faint, Medium, Strong, and Very Strong.
Learn moreFracture Filling
A clarity treatment in which a glass-like substance is injected into surface-reaching fractures to reduce their visibility.
Learn moreFTIR
Fourier-transform infrared spectroscopy, used to classify diamond type (I/II) and detect certain treatments.
Learn moreHue
The dominant spectral colour of a fancy coloured diamond, such as blue, pink, or yellow.
Learn moreIrradiation
A treatment using electron or neutron bombardment to alter a diamond’s colour, often followed by annealing.
Learn moreKarat (Gold)
A measure of gold purity (24kt = pure gold). Not to be confused with diamond carat.
Kimberley Process
International certification system preventing the trade of conflict diamonds.
Learn moreLaser Drilling
A clarity treatment that uses a focused laser beam to create a channel to reach and bleach dark inclusions.
Learn moreLaser Inscription
A micro-engraving on the girdle of a diamond, typically the laboratory report number, used for identification.
Learn moreMeasurements (mm)
The length, width, and depth of a diamond recorded in millimetres on a grading report.
Learn moreMelee
Small diamonds (under 0.2 ct), often used as accent stones.
Milky Diamond
A diamond with reduced transparency caused by sub-microscopic inclusions or structural irregularities.
Learn moreOverweight Diamond
A diamond cut deeper than ideal proportions to retain carat weight, resulting in a smaller face-up appearance.
Learn morePavilion
The lower part of a diamond below the girdle — reflects light back through the crown.
Learn morePavilion Angle
The angle between the pavilion main facets and the girdle plane, critical for light return and brilliance.
Learn morePhotoluminescence (PL)
A spectroscopic technique using laser excitation to identify defect centres and detect treatments in diamonds.
Learn morePlot
A diagram on a grading report that maps the location and type of a diamond’s clarity characteristics.
Learn morePolish
The quality of a diamond’s surface smoothness resulting from the cutting and polishing process.
Learn moreProportions Diagram
A profile view on a grading report showing key angles, percentages, and measurements of a diamond’s cut.
Learn moreSaturation
The intensity or purity of a fancy diamond’s colour, ranging from weak to vivid.
Learn moreSpread
The face-up size of a diamond relative to its carat weight; a well-spread stone looks larger for its weight.
Learn moreStrain Patterns
Internal stress features visible under cross-polarised light; their character differs between natural and lab-grown diamonds.
Learn moreTable Percentage
The width of the table facet divided by the average girdle diameter, expressed as a percentage.
Learn moreTension Setting
A stone held by the pressure of metal arms — appears to float.
Tone
The lightness or darkness of a fancy coloured diamond’s colour, ranging from very light to very dark.
Learn moreType I / Type II
Scientific classification of diamonds based on nitrogen content and arrangement; Type I contains nitrogen, Type II is virtually nitrogen-free.
Learn moreUV-Vis-NIR
Ultraviolet-visible-near infrared spectroscopy, used to analyse colour origin and detect treatments in diamonds.
Learn moreVVS Clarity
Very Very Slightly Included — minimal inclusions, difficult to see under 10× loupe.
Learn moreWindow Effect
A dark area in the center of a poorly cut stone where light "leaks" through.
Learn more