This Diamond Glossary is presented to you by The Canadian Diamond Buying Guide
4Cs, 4C’s The four main quality aspects for consumers to consider when buying diamonds
58 There are 58 facets on a round brilliant cut diamond, including the culet.
100 Points 100 points = 1 carat.
Adamas The word diamond comes from the ancient Greek word adamas (αδαμας), meaning unconquerable.
Angle/Angles To achieve maximum brilliance, there are many angles which are important in diamond cutting. Angles determine proportion.
Baguette A rectangular or oblong step or trap cut used for diamonds and other gemstones.
Balance A diamond balance is any scale or balance specially designed for weighing diamonds, and is calibrated in carats, often with a resolution of 1/1000 of a carat.
Bearded, Bearding Small stress cracks around the girdle caused by bruting (rounding) too quickly or with too much force.
Bezel Generally as rim or sloping side. The bezel facets of a diamond are also known as kite facets.
Black Star of Africa At over 200 carats, this is about the 11th largest diamond in the world.
Black Probably the least attractive colour for diamond, although there seems good demand for treated black diamonds. The main attraction surely being the excellent surface lustre. Black is technically the complete absence of any colour. Many black diamonds have poor surface quality and are probably partially carbonado.
Blue A very rare and valuable colour for diamonds. All natural blue diamonds are type 2b, and contain traces of boron.
Blemish An external mark or imperfection on a diamond, implicitly only slight and capable of being removed.
Blocker, Blocking Diamond cutter who grinds or cuts the first 18 facets being table, culet, and first eight facets on the crown and pavilion. A brillianteer polished the final 40 facets.
Blood Diamond Another name for Conflict Diamond.
Body Colour The colour of light seen through a diamond without any dispersion, usually viewed through the side of a stone. A diamond’s actual colour.
Brilliance The brightness and sparkle of a diamond, not to be confused with its fire or dispersion.
Brilliant Cut A diamond cut using modern facetting layouts, as described by Tolkowsky and others, with 58 facets. Normally round, but there are modified variants in other shapes.
Brown Attractive or vivid brown diamonds are rare, and classed as fancy coloured, slightly brownish stones (off-white) are slightly less common than slightly yellow, and offer reasonably priced alternatives to colourless stones.
Canada Diamond prospecting started in Canada in the 1960’s or earlier, kimberlite was found in the 1990’s, and the first commercial mine opened in 1991. Canada now produces over 12 million carats annually worth over $2 billion according to some sources.
Canary Popular name for a vivid fancy yellow diamond.
Carat, Carats Defines and explains the terms carat and carats as applied to diamonds other gemstone and gold alloys.
Carat Weight The weight of diamonds is measured in carats, a metric carat being a fifth of a gram.
Carbon Diamonds are composed entirely, or almost entirely, of carbon.
Carbon Spot A misnomer. As diamonds are composed almost entirely of carbon, any black spots in them are unlikely to be carbon.
Carbonado Imperfectly or partially crystalised diamond.
Cavity A hole or void in a diamond or other gemstone, either internal or extending to the surface. Internal cavities may naturally contain gas, liquid, solid, a combination of two or three of these, and there may be phase changes depending on ambient temperature.
Certificated A diamond which has been graded and certified or certificated by a gemmological laboratory.
Documents issued by gem labs attesting the genuineness and stating the quality of a diamond or other gemstone.
Certified A diamond which has been laboratory graded, and certified as to quality. We offer certified diamonds for sale.
The clearness, purity, absence, or presence of inclusions in a diamond.
Clean An word used informally to mean flawless, or at least to infer flawlessness.
Cloud Area with many microscopically small inclusions but which impair clarity.
Some low clarity diamonds with significant cloudy or milky areas get sold to consumers with a limited knowledge.
One of the 4 C’s affecting diamond quality and price. Colourless gets promoted as the best, but only because other attractive colours are extremely rare.
Colorimeter A proprietary machine for grading diamond colour.
Fancy coloured diamonds are rare, attractive and valuable.
Colourless, Colorless What most people describe as white. Promoted as being the best “colour”, mainly because real colours are so rare that there is little point promoting them.
Critical Angle The angle of incidence of light measured from the normal (90%) beyond which Total Internal Reflection will occur. From diamond to air, this is a very low figure of 24.4°.
Crown The top part of a diamond, above the girdle.
Crown Angle The angle between the girdle and the crown of a diamond (taken as the kite facets).
Crown Height The height or depth of the top part of a diamond, above the girdle.
Crystal A diamond is a large single crystal of carbon.
Cut One of the four C’s of diamond quality. Also a portion of a diamond parcel split at a random point rather than by selection. Used when a buyer wishes to buy a smaller parcel than is being offered by the seller.
Cuts Glass That fact that diamond will cut glass is often cited, by the less knowledgeable, as some kind of proof that something is diamond. A claim often made by snake oil salesmen and other charlatans selling imitations and attempting to impress potential mugs punters customers.
Cutter One who cuts or polished diamonds.
Cutting The process of cutting, grinding, or polishing rough diamonds into finished goods.
Deep Usually meaning a diamond which has been cut too deep which maximises weight, but sacrifices brilliance. Also refers to deep mines.
Depth The height of a diamond from top to bottom, table to culet.
Density Density is defined as the ratio of the mass of an object to its volume. The density of diamond is 3.52 grams per cubic centimeter.
D, D. Colour D colour denotes colourless on the GIA scale.
Diamond Diamond is an isomer of carbon. The word diamond is often used incorrectly to describe a lozenge shape. The diamond in baseball refers to the infield or the whole pitch, so named because of its lozenge shape.
Diamonds The plural of diamond. Other meaning include the name of one of the four suits in playing cards, the third-highest ranking suit in contract bridge. Diamonds is also the title of a 1975 movie (film) with Robert Shaw and Shelley Winters, and a 1999 movie with Kirk Douglas and Dan Aykroyd.
Durable, Durability Diamond is one of the hardest, toughest, and most durable of substances.
Emerald Cut A square of rectangular shape with cut (mitred) corners, forming an eight sided figure (octagon), and step cut; derives it name because it is the commonest shape of cut for emeralds. Looks glassy, and modern facetting styles such as radiant cut produces more brilliant and attractive stones.
Exceptional White The name of the top colour in the CIBJO colour grading scales, equating to D and E colours in the GIA scale.
Eye Clean No visible inclusions with the human eye, therefore at least SI in clarity.
Facet, Facets The flat surface or planes of a polished diamond.
Fifty Eight Facets The number of facets on a brilliant cut diamond, including the culet.
Finish A word which is loosely used to imply the quality of polish and symmetry on a diamond.
Fissure A crack, gletz, feather, possibly reaching to the surface.
Flaw In inclusion or other feature which is visible or reduces clarity in diamonds or other gems.
Flawless Without any inclusions or features adversely affecting clarity.
Fluorescence Often mis-spelt as flourescence by those who should know better. The emission of visible light displayed by some diamonds and other gems when viewed in ultra-violet or other light. Cause frequent concern by consumers on discovering that one diamond or more in a cluster glow under “disco” lighting.
The four well-known factors affecting the price of a diamond.
Full Cut With 58 facets, i.e. usually a brilliant cut, and usually round.
GIA, G.I.A. The Gemological Institute of America. Styles itself as the world’s leading authority on diamonds and other gemstones. Market leader for diamond and gem certificates by virtue of its location and size.
Girdle The widest part of most diamonds, the middle between the crown and pavilion. May be rough (matt), polished or facetted. Even if facetted, it is only counted as one facet.
Girdle Facet Any of the facets adjacent to the girdle on a brilliant cut or other diamond, split into upper (crown) girdle facets, and lower (pavilion) girdle facets.
Gold Yellow precious metal used in most jewellery in various alloys.
Golden Jubilee The largest faceted diamond in the world, weighing 545.67 carats.
Grade A recognised measure of an aspect of quality, mainly clarity and colour, but can also be applied to proportion and other aspects.
Grading The process of appraising a diamond, and allocating grades to it.
Green A rare colour of diamond.
Grit Small pieces of rough diamond, used as industrial abrasives, may be natural or synthetic.
Hue An aspect of colour, important factor in viewing and grading fancy coloured diamonds.
I1, I2, I3, Included, Imperfect I1, I2, and I3 are all grades in the GIA clarity scale.
Ideal, Ideal Cut Theoretically perfect cutting proportions for (round brilliant cut) diamonds. Exact specifications vary. Many mathematical models ignore girdle thickness.
Inclusion An internal feature or imperfection which reduces the clarity or brilliance of a diamond.
Internally Flawless, IF, I.F. A clarity grade which allows for naturals or other surface features or imperfections.
Investment Although a diamond purchase may prove to become a good investment. Our advice is to buy diamonds for the pleasure they invoke by their ownership and use. Because diamonds are not a homogenous commodity, the secondary market in them is not particularly liquid, compared with that for any other commodity.
Karat, Karats, Karat Weight Karat is the American spelling of carat, although it appears to be used more in respect of gold alloys, whereas the English spelling carat is often used relating to the weight of diamonds or other gemstones.
Light Because of its high dispersion and refractive index, diamond handles light in a characteristic way.
Light Yellow A grade of fancy yellow diamond.
Light, Standard For viewing and appraising diamonds, a standardised light source is desirable. There are lamps which are sold as diamond lights, and at least one specification a standardised light source, and colour temperature.
Loose Unmounted diamond.
Lower Girdle Facet A diamond facet adjacent to and below the girdle (on the pavilion).
Luminescence Some diamonds luminesce (emit light) when exposed to sunlight or other ultraviolet-light sources. The light the diamonds emit is usually light blue, but yellow, orange, and red luminescence occurs in some stones.
Lustre, Luster The lustre of a diamond is its highly reflective surface sheen due to its high refractive index combined with the highly polished surfaces.
Main Facets The first sixteen facets to be ground onto rough diamonds, apart from the table and culet, also the main pavilion facets (the first eight on the pavilion).
Mauve A colour description used for certain pinkish purple diamonds.
Needle A thin, sharp looking inclusion in a diamond.
Octagon, Octagonal See ‘Emerald Cut’, and ‘Radiant Cut’.
Old Cut Any cut, usually round, predating the modern brilliant cut in style.
One Carat A weight of one fifth of a gram. Any diamond of this weight.
Orange A rare fancy colour of diamond.
Oval A fancy shape of diamond, usually a modified brilliant cut.
P1, P2, P3, Piqué, First, Second, Third Clarity grades of diamond in descending order, The American equivalents are I1, I2, I3. In a piquéd stone, the inclusion or inclusions would be visible to the human eye.
Pavilion The lower part of a diamond, below the girdle.
Pavilion Angle The angle between the main pavilion facets and the girdle. In diamond cutting and proportion, this is the single most important dimension, and should be around 40.75° to 41°.
Pavilion Facet Any of the facets on the pavilion of a diamond, but usually referring to the main pavilion facets, as distinct from the lower girdle facets.
Perfect, Perfection Only D colour and flawless diamonds should be described as perfect. It is our view that perfection is illusory or elusive, as “perfect” diamonds viewed under 20 times magnification instead of 10 times, would probably reveal tiny features or imperfections.
Phosphorescence Some diamonds and other gemstones and minerals continue to glow or emit visible light for a period of time after exposure to visible, ultra-violet or other light, after the light source has been removed.
Photoluminescence The emission of visible light by a diamond due to the incidence of light of a different wavelength, including fluorescence and phosphorescence.
Pink One of the rarest and most desirable colours for diamond.
Point A weight of one hundredth of a carat, written as 0.01 cts. The name of an old basic cut. Any sharp meeting place of three or more facets, such as a corner, or a closed culet; forms a weak point in polished diamonds, as a sharp blow to a point could easily cause the diamond to cleave (break).
Polish, Polished, Polishing In diamond manufacturing, polishing can refer to the grinding of facets onto a partially made rough diamond, but more particularly the later stages of brillianteering.
Polished Girdle A girdle which had been finely ground to a polished finish instead of the older and simpler matt finish left by bruting.
Polish Lines Faint surface lines visible either as a result of imperfect polishing, or of grain lines in the diamond.
Princess A square or near square (oblong) diamond, which has been facetted in a brilliant cut style rather than a step cut.
Proportion The consideration of the overall shape of a diamond taking each part in relation to all other parts. An important quality element for diamonds.
Proportionscope A proprietary piece of equipment for assessing, demonstrating, and measuring the proportions of diamonds, and comparing them with ideal.
Purity Another word for clarity.
Purple A very rare and attractive fancy diamond colour.
Quartz Sometimes used a an imitation or simulant for diamond, particularly the transparent colourless form known as rock crystal.
Radiant Cut Radiant cuts combine the best of brilliant cuts, with a square emerald cut outline.
Red One of the rarest, and most desirable colours for diamond.
Rough Rough is the word used to describe all uncut or unpolished diamonds.
Semi Precious, Semi-Precious An expression traditionally used to describe gemstones other than the “big four” of diamond, ruby, sapphire, and emerald, so would include opal, pearl, amethyst an more. CIBJO and others have advised that its use be discontinued, and all gemstones be termed “precious”, a recommendation which has been almost universally ignored.
Set The process of securing a diamond or other gem into a piece of jewellery is known as setting it.
Setter Person who puts diamonds or other gems into jewellery mounts.
Setting The process of fixing a gemstone into a mount to create a piece of jewellery. A setting is a word used by consumers to describe what a jeweller would call a mount. The word setting is sometimes used in referring to a collet.
Shape A word often used interchangeably with “cut”, although the two have different meanings. Shape should refer to the basic outline type, such as round, oval, square, princess, radiant, cushion, oblong, emerald, baguette, pear.
Shapes A term used when sorting rough diamonds. “Shapes” are unbroken crystals, but of less regularity than “stones”.
Single Cut Confusingly, another name for eight cut diamonds, with 18 facets.
Single Refraction Diamond is normally singly refractive, many gemstones are doubly refractive (bi-refringent), and diamonds can also be doubly refractive because of internal strain or inclusions.
Slight Inclusions, SI, SI1, SI2 A clarity grade used by GIA and others, an SI stone should not have inclusions visible to the human eye.
SI3 A clarity grade between SI2 and P1 (I1), not recognised as yet by the GIA, but in use by EGL and Rapaport, plus most of the wholesale diamond trade.
Small Slightly variable term used to describe size ranges of polished diamonds, usually meaning any weight under about 0.08 cts (8 points).
Solitaire A ring or other piece of jewellery containing a single diamond, or sometimes a single major diamond with smaller diamonds as embellishments.
Spotted A clarity grade below P3 (I3), now in danger of become obsolete, as P3 appears to have been extended to include lower grades.
Spread The diameter of a diamond or the normal weight equivalent assuming ideal proportions. Also used to describe a diamond which is cut too shallow, and therefore “spreads” more than it weighs.
Star A fancy shape of polished diamond. A facet name. Small polished diamonds, usually under about one point (0.01 cts) each.
Star Facet One of the eight facets adjacent to the table on a brilliant cut diamond, so called because they from an eight pointed star when viewed from above.
Stars Small polished diamonds, usually under about one point (0.01 cts) each.
Step Cut A traditional method of facetting square, emerald and other shapes, the facets are in the form of sloping “steps”, these cuts fail to capture most of the potential brilliance of diamonds, and will almost certainly be largely superseded by modified brilliant styles of cutting.
Stone, Stones A general word for any gemstone including diamond. Also a shape grade used when sorting rough diamonds. A “stone” is an unbroken crystal of regular formation.
Sunflower Cut One of a number of “flower cuts” developed by Gaby Tolkowsky in about 1997 for De Beers.
Table Facet The top and largest facet on most diamonds including brilliant cuts.
Thermoluminescence The property of diamonds and other materials to emit light when heated.
Thickness Usually describing a girdle, and often expressed as a percentage of the height or depth of the diamond, often using relative terms such as “medium”.
Tone An aspect of colour, important in grading fancy coloured diamonds.
Top The part of the diamond above the pavilion, correctly called the “crown”. Also a modifier used in descriptive colour grading systems, meaning better than or in the upper range of , e.g. top silver cape.
Top Light Brown A relatively lightly coloured brownish diamond, often bordering on white.
Transparent, Transparency Ideally, a diamond should be completely transparent, any opacity is undesirable.
Trap Cut Also known as step cut. A traditional way to cut rectangular, octagonal or other non-round diamonds, including emerald cuts. Looses brilliance compared with more modern brilliant cut styles.
Uncut Uncut diamonds are usually referred to as “rough”. It applies to all unpolished diamonds.
Unpolished Unpolished diamonds are usually referred to as “rough”. It applies to all uncut diamonds.
Unmounted A diamond which is loose, not set in a piece of jewellery.
Upper Girdle Facet Any of the sixteen facets on the crown (top), adjoining the girdle of a diamond.
VS, V.S., Very Slight Inclusions, VS1, VS2 Clarity grade for diamonds, between VVS and SI.
VVS, V.V.S., Very Very Slight Inclusions, VVS1, VVS2 Clarity grade for diamonds, just below Internally Flawless (I.F.)
Weight, Weights The weigh of any diamond is normally expressed in carats.
White When we rather lazily refer to diamonds as white, we actually mean colourless.
Yellow Most diamonds contain nitrogen which gives them a slight yellow tinge. More intense yellow diamonds are considered as fancy coloured, making them rare and valuable.
Zircon Rare, natural blue gemstone. Do not confuse it with Cubic Zirconia.
Zirconia Usually referring to Cubic Zirconia.