A diamond looks like any other rock until it is cut to produce maximum brilliance and fire. Here’s a glossary of terms commonly used in the industry with reference to diamond cuts and properties.
AbrasionTiny nicks along the facet junctions, producing white fuzzy lines instead of sharp crisp facet edges.
Asscher cut: Fancy diamond with the shape of a square emerald cut. Developed in the early 1900s by Asscher, a diamond cutter from Amsterdam.
Baguette Cut: A step cut in the shape of a small rectangular diamond. May be tapered on one end.
Bearding: Tiny, numerous hair-like fractures extending into the diamond.
Bezel: A facet on the crown, or upper part of the diamond, but the girdle.
Blemish: Surface imperfection on a diamond.
Bort: Industrial grade diamonds, diamonds not suited as jewels.
Bow Tie: An effect caused by a shadowy areas visible in some fancy shapes (like ovals and pears), caused by light leaking out of the bottom of the diamond.
Brilliant Cut: The most common cut, round, containing 57 or 58 facets, also called the Round Brilliant Cut.
Bruise: An inclusion consisting of a surface crumbling, often accompanied by tiny root like-like feathers.
Carat: The metric “carat”, which equals 200 milligrams, is the standard unit of weight for diamonds and most other gems.
Carat Spread: The difference in weight between and ideally cut stone and a less perfectly cut stone with the same outer dimension (diameter of the girdle). Often used to help sell stones that are shallow cut, meaning the stone is short and fat, which makes the stone appear larger while weighing less.
Carbon Spots: A term sometimes used to describe the appearance of certain inclusions in a diamond.
Cavity: An inclusion consisting of a large or deep opening in a diamond.
Certificate: Laminated document by a gemological institute (ie. GIA, AGS, EGL) to describe a diamond’s characteristics.
Chip: A tiny, missing piece, caused by normal wear and tear, or by cutting.
Clarity: Also known as purity. A diamond’s relative position on a flawless to imperfect scale based on the number and location of imperfections inside the diamond. The clarity scale goes from FL-IF to varying degrees of imperfect.
Cleavage: The propensity of crystalline minerals, such as diamond, to split in one or more directions, either along or parallel to certain planes, when struck by a blow. Cleavage is one of two methods used by diamond cutters to split rough diamond crystals in preparation for the cutting process. Sawing is the other method.
Cloud: A group of tiny white inclusions which result in a milky or cloudy appearance.
Color: Color refers to the amount of body color a diamond has, most commonly yellow or brown, but also rarely in pink, green, blue, orange, and fancy yellow. The color of a diamond is an important characteristic because it is noticeable to the untrained eye.
Crown: The portion of the stone above the girdle.
Crown Angle: The angle at which a diamond’s bezel facets (or, on emerald cuts, the row of concentric facets) intersect the girdle plane.
Culet: The facet on the bottom of tip of the diamond. A diamond with no culet has a pointed tip. A diamond with a small culet has a flat surface at the tip. Culets can prevent chipping but can be less desirable when in the medium to large range. A diamond with a medium to large culet will appear to have a hole in the bottom when looking down the stone, through the table.
Cushion Cut: A fancy cut with rounded corners and larger facets. Sometimes also referred to as a pillow cut.
Dahlia Cut: Oval with flat ends, total of 51 facets: 37 facets on the crown, 14 facets on the pavilion. “Invented” or DeBeers in the 90s by Antwerp cutter Gabi Tolkowsky.
Depth: The height of the diamond from the culet to the table. The depth percentage listed on the certificate indicated the height of the diamond relative to the width measurement (height value, width value). A diamond which is too shallow or too deep will disperse light through the sides or the bottom instead of the top.
Eight Cut: Also called “single cut”, usually restricted to melee (very small diamonds) have less facets, 17 or 18, than a full brilliant cut.
Emerald Cut: Step cut diamond, usually rectangular shape and cut corners. The ideal length to width ratio of the emerald cut is between 1.5 and 1.7.
Eye Clean: A diamond with no inclusions visible to the naked eye without the aid of a loupe.
Extra Facet: A “false” facet, a facet placed without regard for symmetry and not required by the cutting style.
Facet: A plane, polished surface of a diamond. The brilliant, a full cut round diamond, usually contains 58 facets.
Faceted Girdle: Some cutter also polish the girdle for maximum reflection, into 32 facets for a round diamond.
Fancy: A diamond with another shape other than round cut (ie. princess, emerald, oval, cushion etc.) and/or with an attractive natural body colour other than light yellow or light brown.
Feather: A separation or break due to either cleavage or fracture, often white or feathery in appearance.
Flaw: An imperfection in a diamond, see clarity.
Finish: Refers to qualities imparted to a diamond by the skill of the diamond cutter. It covers every aspect of the diamonds appearance that is not a result of the diamond’s inherent nature.
Fluorescence: A naturally occurring glow some diamonds exhibit under ultraviolet lighting conditions, normally bluish in color but can also be yellow.
Fluorescence Ratings: None, faint, slight, medium, strong blue, very strong blue. Strong blue and very strong blue fluorescence may cause the diamond to appear milky in daylight. According to the GIA, only .2% of diamonds with fluorescence will exhibit a milky appearance in sunlight. Fluorescence can raise the color appearance by several grades and give a diamond a slight blue tint in certain lighting.
Fracture: A crack on the diamond’s surface.
Girdle: The outer edge of the widest part of the diamond, forming a band around the diamond. Some cutters also polish the girdle into facets for maximal reflection.
Grain: A small area of concentrated crystal structure distortion, usually associated with pinpoints.
Green: A rare natural fancy colour from lime to intense green. Radiation treated diamonds may also have a green colour variation.
Hardness: Mineral’s resistance to scratching on a smooth surface. Measured on the Mohs scale of hardness ranging from 1-10. Diamond measure 10 on the Mohs scale and is the hardest of all gemstones.
Hearts & Arrows Cut: A perfectly symmetrical round brilliant diamond with 58 facets. Under special illumination, the H&A cut diamond presents a pattern resembling hearts and a star of arrows the same length and width.
A type of fancy diamond cut, which is cut ot resemble the popular Valentine’s Day shape.
Inclusion: Imperfection internal to the diamond, the unique “birthmark” of a diamond. Inclusions tend to viewed with a 10x loupe, or greater, and affect the diamond clarity. No two diamonds have the same position, size, and colour of an inclusion.
Internal Graining: Internal indications of irregular crystal growth. May appear milky, like faint lines or streaks, or may be coloured or reflective.
Kimberlite: Complex, pipe-shaped mixture of rock material, formed by solidifying volcanic magma. Not the actual source for diamonds, but the “elevator” that brings them to the Earth’s surface. The name is derived from South Africa's Kimberly Mine, where this phenomena was discovered.
Knot: An included diamond crystal which reaches the surface of a polished diamond.
Laser Drill Hole: A tiny tube made by a laser to remove an inclusion, noticeable on clarity enhanced diamonds. The surface opening may resemble a pit, while the tube usually looks needle like.
Laser Identification: Microscopically smaller superficial inscription created by a laser on a diamond for identification. Relatively easily to remove by polishing.
Marquise Cut: A modification of the brilliant cut, it is a boat shape, elliptical and pointed at both ends. It is sometimes described in old valuations as Navette.
Melee: Small diamonds under .20 carat, usually .10 carat or under, often as small as .8mm in diameter. Can be either fully faceted with 57 facets or single cut.
Mixed Cut: A stone with either the crown or the pavilion cut as a brilliant cut, and the other part as a step cut.
Natural: Part of the rough diamond remaining on a diamond, having survived the cutting process.
Needle: A long, thin included crystal which looks like a tiny rod.
Nick: A notch near the girdle or a facet edge.
Off Make: A poorly proportioned diamond.
Old European Cut: Early round cut, the predecessor to the brilliant cut. The OEC is comprised of chunky facets, a small table, an open culet, and a high crown.
Oval Cut: Cutting shape of a diamond, oval with facets.
Pavillion: The lower portion of the diamond, below the girdle.
Pear Shape Cut: Also referred to as tear drop shape.
Pendeloque Cut: A modification of the brilliant cut, with the stone cut into a pear shape.
Pink: A very rare natural fancy colour. Radiation treated diamonds (not natural) can also create a pink colour variation.
Pink Star: A 59.60 carat fancy vivid pink diamond which set the new world auction record price for any diamond, gemstone, or jewel at Sotheby’s Geneva when it sold for $83.2 million. The new diamanaire owner renamed it “Pink Dream”.
Pit: A tiny opening, often looking like a white dot.
Points: Pts, 1pt is 100th of a carat, or 0.01ct, like a penny to a dollar.
Polish Lines: Tiny parallel lines left by polishing. Fine parallel ridges confined to a single facet, caused by crystal structure irregularities, or tiny parallel polished grooves produced by irregularities in the scraped surface.
Polish Marks: Surface clouding caused by excessive heat (also called burn mark, or burned facet), or uneven polished surface resulting from structural irregularities.
Premier: A diamond with a yellowish body colour which is masked by a strong blue fluorescence. The diamond will appear whiter than it actually is, but could have an oily or milky appearance in daylight or fluorescent light. The value of the stone is reduced.
Princess Cut: Normally a square diamond with a faceted base. It is the square equivalent to a round brilliant.
Radiant Cut: A type of brilliant cut fancy shape that resemble a square or rectangle with the corners cut off.
Ratio: A comparison of how much longer a diamond is than it is wide. Used to analyze the outline of fancy shapes. Not applied to round diamonds.
River: Infrequently used reference for the colour of a diamond, ie River = D and E white. River refers to the colour D, exceptionally white.
Round Cut: The most common cut, usually containing 58 facets. Also the most brilliant cut in terms of the most efficient use of light to increase brilliance and fire, hence the name “brilliant”.
Rose Cut: A stone cut with a flat base, with the upper facets cut to a point. Normally encountered in antique jewelry starting with the 17th century, but making a comeback in the last few years.
Scratch: A linear indentation normally seen as a fine white line, curved or straight.
Simulant: Any diamond-like material, either natural or artificial, which is marketed as a look-alike for a natural diamond. ie, glass, zirconium, YAG, GGG, moissanite, etc. Not to be confused with synthetic.
Single Cut: A very small round diamond with only 16, 17, or 18 facets, instead of the normal 57 or 58 facets of a full cut round brilliant. Used mostly for pave jewelry.
Spread Cut: A diamond with a large table and a thin crown height.
Step Cut: One of three styles of faceting arrangements with three concentric rows of facets arranged around the table and three concentric rows around the culet. Baguette cuts (straight or tapered), emerald cuts, and asscher cuts are all step cuts.
Surface Graining: Surface indication of structural irregularity. May resemble faint facet lines, or cause a grooved or wavy surface. They often cross facet junctions.
Synthetic Diamond: Man made, or lab grown, unlike a simulant, has the identical chemical composition and crystal structure as the natural counterpart.
Symmetry: Describing small variations in a diamond’s symmetry, such as misalignment of facets or facet that fail to point correctly to the girdle. An indicator of the quality of the diamond’s cut, graded as either ideal, excellent, very good, good, fair, or poor.
Table: The flat facet on the top of the diamond. It is the largest facet on a cut diamond.
Table Percentage: The value which represents how the diameter of the table facet compares to the diameter of the entire diamond. A diamond with a 60% table has a table which is 60% as wide as the diamond’s outline.
Tone: A diamond’s colour position on a colourless to black scale.
Top Wesselton: Refers to colours F and G on the diamond colour scale. Some may also call colour F a Top Wesselton+.
Treated Diamonds: Fancy colour treatment: a diamond with a body-colour induced some some for of artificial irradiation, often in conjunction with controlled heating (known as annealing). Other possible treatments of diamonds are: coating, fracture filling, spot bleaching by laser, HPHT (high pressure high temperature) whitening, electromagnetic conduction whitening.
Trilliant Cut: A type of brilliant fancy shape that is triangular.
Twinning Wisp: A cloudy area produced by crystal structure distortion, usually associated with twinning planes.
Van Graff: A diamond simulant made of Yttrium Oxide enhanced CZ. Mohs hardness is 8.7
Wesselton: Originally the name of a diamond mine producing white diamonds. Nowadays a less used reference for the colour of a diamond. Wesselton is H coloured. Top Wesselton refers to colours F and G, and some may also call F a Top Wesselton+.