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Diamond Glossary

Choosing diamond jewellery can seem overwhelming if you're not familiar with some of the terms jewellers use when they talk about diamonds. This glossary contains all the important words you might hear from a jewellery when you're picking out a diamond.

Asscher Cut: A square emerald cut - wide corners, high crown and deep pavilion.

Baguette: A small, rectangular-to-square step-cut diamond.

Blemish: A clarity attribute that transpires on the surface of a diamond. Though some blemishes are natural to the original rough diamond, most are the result of the environment the diamond has experienced since it was unearthed.

Brilliance: The brightness that appears to come from the heart of a diamond. With a level that is unique to diamonds, other gemstones possess lesser levels and don't have the ability to equal the extent of diamond's light-reflecting power. Brilliance is produced primarily when light makes its way into the table, reaches the pavilion facets, and is then reflected back out through the table, where the light is most visible to your eye.

Brilliant Cut: One of three variations of faceting layouts. In this type of arrangement, all facets appear to radiate out from the centre of the diamond toward its external edges. It's called a brilliant cut because it is designed to maximize brilliance. There are a number of brilliant cuts like round diamonds, ovals, radiant, princesses and more.

Carat Weight: The unit of weight by which a diamond is measured. One carat equals 200 milligrams, or 0.2 grams originating from the use of carob beans to measure the weight of gemstones.

Carbon Spots: This term refers to imperfections called included crystals that have a dark appearance, rather than a white or transparent appearance, when viewed under a microscope.

Carr Cut: A square step-cut diamond.

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 the two methods used by diamond cutters to split rough diamond crystals in preparation for the cutting process (sawing is the other method).

Clouds: A grouping of a number of tiny inclusions that is too small to be distinguishable from one another, even under magnification. Not visible by the naked eye, they look like a soft, transparent cloud under a microscope.

Cognac Diamond: Brown coloured diamond, also called Champagne Diamond

Colour Grading: A system of grading diamond colour based on their colourlessness (for white diamonds) or their spectral hue, depth of colour and purity of colour (for fancy colour diamonds).

Crown: The upper portion of a cut gemstone, which lies above the girdle. The crown consists of a table facet surrounded by either star and bezel facets (on round diamonds and most fancy cuts) or concentric rows of facets reaching from the table to the girdle (on emerald cuts and other step cuts).

Crown angle: The angle at which a diamond's bezel facets intersect the girdle plane. This gentle slope of the facets that surround the table is what helps to create the dispersion, or fire, in a diamond.

Culet: A very small flat facet that diamond cutters commonly add at the base of a diamond's pavilion. Its purpose is to protect the tip of the pavilion from being chipped or damaged.


Cut: This refers both to the proportions and finish of a polished diamond. As one of "the Four Cs" of diamond value, it is the only man-made contribution to a diamond's beauty and value.

Cushion-Cut: Modified brilliant-cut diamond with curved sides and rounded corners.

Depth: The height of a diamond from the culet to the table.

Depth Percentage: On a diamond grading report, you will see two different measurements of the diamond's depth-the actual depth in millimetres (under "measurements" at the top of the report) and the depth percentage, which expresses how deep the diamond is in comparison to how wide it is. This depth percentage of a diamond is important to its brilliance and value; where that depth lies can be equally important.

Diamond: A crystal made up of 99.95% pure carbon atoms arranged in an isometric crystal arrangement. Diamonds are made of pure carbon and crystallised deep in the earth due to intense pressure and heat, over billions of years. Diamonds, by pure miracle, are brought closer to the Earth's surface through volcanic eruptions.

Diamonds are the hardest, most imperishable, and the most brilliant of the gemstones

Diamond Cutting: The method by which a rough diamond that has been mined from the earth and shaped into a finished, faceted stone.

Diamond Gauge: An instrument used to measure a diamond's length, width and depth in millimetres.

Dispersion: Also known as "fire" it the manner in which the light is broken and reflected. Components of light are broken into spectral colours (for example, red, blue and green and appears as a play of small flashes of colour across the surface of the diamond as it is tilted.

Emerald-Cut: A square or rectangular-shaped diamond with cut corners.

Eye-Clean: A jewellery industry term to describe a diamond with no blemishes or inclusions that are visible to the naked eye.

Facet: The smooth, flat faces on the surface of a diamond. They allow light to both enter a diamond and reflect off its surface at different angles, creating the wonderful play of colour and light for which diamonds are famous.

Fancy Shape: Any diamond shape other than round.

Feathers: These are small fractures in a diamond.

Finish: This term refers to the qualities imparted to a diamond by the skill of the diamond cutter. The term "finish" covers every aspect of a diamond's appearance that is not a result of the diamond's inherent nature when it comes out of the ground.

FL (Flawless): Diamonds with no internal or external blemishes or inclusions.

Fluorescence: An effect that is seen in some gem-quality diamonds when they are exposed to long-wave ultraviolet light.

Four Cs: A diamond's four characteristics: Cut, Colour, Clarity and Carat Weight.

Gemmological Institute of America (GIA): Founded in 1931 by Roger Shipley, this non-profit organization upholds the standards for grading diamonds and is one of the most-respected and well-regarded gemmological laboratories in the world. They are geniuses when it comes to lab-grown diamonds. 

Girdle: The outer edge, or outline, of the diamond's shape.

Hardness: A diamond's resistance to scratching and abrasion.

Heart-shape Cut: A type of fancy diamond cut, which is cut to resemble the popular Valentine's Day shape.

IF (Internally Flawless): Diamonds with no internal blemishes or inclusions.

Inclusion: A clarity characteristic found within a diamond. Most inclusions were created when the gem first formed in the earth.

JAA: The Jeweller's Association of Australia.

Laser-Drill Holes: One of the few man-made inclusions that can occur inside a diamond. An intentionally created inclusion can actually raise its clarity grade.

Length-to-Width Ratio: A comparison of how much longer a diamond is than it is wide. It is used to analyse the outline of fancy shapes only; it is never applied to round diamonds.

Loupe: A small magnifying lens used to examine a diamond.

Lustre: The surface appearance of a polished diamond under reflected light.

Marquise-Cut: A type of fancy shape diamond which is elongated with points at each end.

Modified Brilliant Cut: Round brilliant cut, with more or less facets than standard.

Naturals: Small parts of the original rough diamond's surface which are left on the polished diamond, frequently on or near the girdle.

Oval-Cut: A type of fancy shape diamond which is essentially an elongated version of a round cut.

Pav: A style of jewellery setting in which numerous small diamonds are mounted close together to create a glistening diamond crust that covers the whole piece of jewellery and obscures the metal under it.

Pavilion: The lower portion of the diamond, below the girdle.

Pear-Cut: A type of fancy shape diamond that resembles a teardrop.

Point: A unit of measurement used to describe the weight of diamonds. One point is equivalent to one-hundredth of a carat.

Polish: Refers to any blemishes on the surface of the diamond which are not significant enough to affect the clarity grade of the diamond.

Princess-Cut: A type of brilliant cut fancy shape that can be either square or rectangular.

Radiant Cut: A type of brilliant cut fancy shape that resembles a square or rectangle with the corners cut off.

Ratio: A comparison of how much longer a diamond is than it is wide.

Rose Cut: Old cut characterised by a flat base, a circular girdle, and pointed crown.

Rough Diamond: A diamond from the earth prior to cutting and polishing.

Round Brilliant Cut: Round cut diamond with a circular girdle and 57 or 58 facets.

Semi-Mount: A jewellery setting that has the side stones already mounted, but which contains an empty set of prongs which are intended to mount a diamond centre stone that the customer selects separately.

Single-Cut: A very small round diamond with only 16 or 17 facets, instead of the normal 57 or 58 facets of a full cut round brilliant.

Solitaire: A ring that usually has a single diamond.

Step Cut: One of three styles of faceting arrangements.

Symmetry: Refers to variations in a diamond's symmetry. The small variations can include misalignment of facets or facets that fail to point correctly to the girdle (this misalignment is completely undetectable to the naked eye). Symmetry is regarded as a quality indicator of a diamond's cut; it is graded as 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.

Tapered Baguette: Rectangular baguette where one end is narrower than the other

Trilliant-Cut: A type of brilliant fancy shape that is triangular.

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