When the culet becomes chipped or scratched by another diamond.
A bruise or scratch on a polished diamond.
AGS - American Gem Society
Diamond grading laboratory.
Mining for diamonds that have been carried by wind and water down rivers over million.
A documented estimate by experts, of the approximate retail value of a diamond or piece of jewellery. Appraisals are usually used for insurance purposes to estimate replacement value. Do not confuse with a diamond certificate or report.
The diamonds produced by the Argyle mine are found in a range of colours including white, champagne and pink. Argyle is the world's primary source of rare pink diamonds, which have become Argyle’s signature stone.
A square cut diamond with 58 step cut facets. Also called a square emerald.
Diamond grading laboratory.
A rectangular shaped diamond (may also be tapered). Characterised by square corners with rows of step-cut facets parallel to the table. Baguettes are often used as enhancements or side stones to a larger centre stone.
Bearding / Bearded Girdle
Tiny hair-like lines that can occur around the girdle during the cutting process. Minimal bearding is usually not a problem.
The kite shaped facets on the crown that sit between the table and the girdle.
In a bezel setting, a metal rim holds the diamond and surrounds the stone above the girdle. Bezel settings are considered safe and secure mounts.
Natural "Black" diamonds are not truly black; rather they contain numerous dark inclusions that give them their dark appearance.
An external clarity characteristic that can be seen on the surface of a diamond. Though some blemishes are inherent to the original rough diamond, most are the result of the conditions in which the diamond was kept and handled after being polished.
see Conflict Diamonds
Natural blue diamonds contain the element boron which give the diamond a distinct blue body colour.
Very low quality diamond, usually used for industrial purposes. Can be crushed to powder and mixed with fine oil to form a paste and then applied to the scaife.
A meeting place where diamond dealers meet to transact business; a trading floor.
A dark area across the centre of a fancy shaped stone, common in oval, marquise and pears, detracting from value.
The aspect of light return in a diamonds appearance that is most immediately noticed. Brilliance is created primarily when light enters through the table, bounces about on the pavilion facets, and is then reflected back out through the table. An aspect for which the desired outcome is obvious - Bright is good and dark is not.
The style of cutting a diamond with multiple facets in a particular way designed to maximise brilliance.
The initial process of rounding a diamond by grinding against another diamond on a rotating wheel.
The four main characteristics that define the quality of a polished diamond: Carat, Colour, Cut and Clarity.
An out of date diamond industry trade term referring to a diamond of yellowish tinge; this is not a reliable colour grade.
One of the 4Cs. The unit of measuring the weight of diamonds. One carat is equivalent to 200 milligrams or 1/5th of a gram. One carat can also be divided into 100 'points'. A 0.75carat stone is the same as 75 points or a ¾ carat stone. The word carat comes from the carob bean, whose consistent weight was used in ancient times to measure gemstones.
Square shape step cut diamond whose corners are not truncated.
Produced by a gemological laboratory for a fee to accurately and objectively determine diamond quality. Do not confuse with a valuation.
An alternative way of describing fancy coloured brown diamonds. The diamonds are often graded on a C1-C7 colour scale, ranging from lighter to darker as the number increases. Darker C7 coloured stones are often called Cognac.
A setting style, where two parallel metal walls are used to hold diamonds in place, with no metal showing between each stone.
A tiny missing piece of the diamond, caused by normal wear and tear, or by cutting.
A general term used to refer to the presence of inclusions or blemishes in/on a gemstone.
Evaluating characteristics within (inclusions) and on the surface (blemishes) of a diamond. Clarity involves determining the number, size, relief, nature, and position of these characteristics, as well as how these affect the overall appearance of the stone. A grade based on the relative lack of clarity characteristics is then assigned.
Also known as prongs. Part of the jewellery setting which holds and supports a stone in place.
A grouping of a number of extremely small inclusions that are too small to be distinguishable from one another, even under magnification, that often look like a soft transparent cloud inside the diamond. Usually, this sort of inclusion does not significantly impact a diamond's clarity grade.
Term used to describe high colour rough and polished diamonds.
Diamond colour is all about what you can’t see. Diamonds are valued by how closely they approach colourlessness – the less colour, the higher their value. The colour grading scale for diamonds begins with the letter D, representing colourless, and continues with increasing presence of colour to the letter Z, or light yellow or brown. Each letter grade has a clearly defined range of colour appearance. Diamonds are colour graded by comparing them to stones of known colour under controlled lighting and precise viewing conditions. The exception to this are fancy colour diamonds, such as pinks and blues, which lie outside this colour range.
Part of the GIA colour grading scale that contain the colour grades D, E and F.
A carefully selected set of polished diamonds of known body colour and saturation. Used by diamond grading professionals and laboratories for diamond colour comparison, and to assign colour grades in the normal D-to-Z colour range.
Conflict diamonds are diamonds that originate from areas controlled by forces or factions opposed to legitimate and internationally recognised governments, and are used to fund military action in opposition to those governments, or in contravention of the decisions of the United Nations Security Council.
An old and stable part of the continental lithosphere that may contain diamonds. Having often survived cycles of merging and rifting of continents, cratons are generally found in the interiors of tectonic plates.
The top portion of a faceted gemstone; the portion between the table and the girdle.
The angle of the bezel facet relative to the table facet. The average of all eight crown angles is reported to the nearest half of a degree.
Average crown height relative to the average diameter; measured from the table facet to the intersection of the bezel facet with the girdle, represented as a percentage.
The point on the bottom of a diamond's pavilion is called the culet (pronounced que-let). Historically, during the manufacturing process, the culet was often polished as a flat facet so that it did not get chipped as the other facets were being polished. These days the cutter usually closes this facet to a point. Sometimes you may read on a diamond certificate that a round brilliant cut has 57 facets, and sometimes 58; the 58th facet is the culet.
Square or rectangular brilliant cuts with rounded corners and curved sides. As with other fancy shapes, Cushion cuts cannot be defined by numbers like a round brilliant, therefore there are multiple variations, and personal preference is key.
Is about how well a diamond's facets interact with light. The quality in design and craftsmanship (as evidenced by a diamond's weight ratio, durability, polish, and symmetry) and face-up appearance are considered in a diamond's final cut grade. Only available for round brilliant shapes at this time.
Cutting & Polishing
The process of preparing a rough gem-quality diamond so that it can be used in the manufacturing of jewellery.
Dense Medium Separation
Diamonds are heavier than the material that surrounds them. Once the ore has been crushed to a manageable size, it's mixed with a slurry prepared to a specified density. In the method known as Dense Medium Separation which exploits the relative densities of different materials, centrifugal force is applied to separate out a diamond-rich concentrate.
The height of a diamond from the culet to the table. The depth is measured in millimetres.
The depth of a diamond (table to culet) divided by the width of the diamond, represented as a percentage. Expresses the proportion of the depth to the width. The higher the number, the deeper the stone; the lower the number the shallower the stone.
Used in the diamond industry to denote a person who possesses diamond-related skills.
The distance measured between two opposing points along the girdle's outline. The minimum and maximum girdle diameters are determined by taking a number of diameter measurements.
A diamond is the hardest known natural substance. Made up of 99.95% pure carbon atoms, it is crystallised carbon. Diamonds are mined in their rough form and then cut and polished to reveal their brilliance.
Diamond Grading Report
Containing or yielding diamonds.
The industry value chain that runs from consumers and retail stores to jewellery manufacturers, cutters and polishers, back to producers and explorers.
The scientific term for the breaking up of white light into its spectral colours. All polished diamonds have the same dispersion regardless of their shape or proportions. Dispersion is represented by a single value based on a material’s refractive index (RI). Diamond has a refractive index of 2.417.
Attached to the end of a tang, adjustable to angle facets, also holds a pot for the diamond to sit in.
A diamond dossier offers the same grading information as a regular diamond grading report but without the plotted diagram. Usually used for diamonds weighing less than one carat.
EGL - European Gemological Laboratory
Diamond grading laboratory.
There is not a set definition for this term. It is generally accepted as a diamond industry trade term meaning no visible inclusions, face up at a reasonable distance in natural lighting to a person with 20/20 vision without the aid of magnification.
Clarity Enhancement is any process used to improve the apparent clarity of a diamond. This may include filling fractures and cavities with glass or resin. It is unethical to promote an enhanced diamond as an untreated diamond.
A round brilliant cut made to a high standard of make and finish.
Polished on to a stone to reduce or hide an imperfection.
Diamond facets are the smooth surface areas of a diamond which have been cut, polished and positioned at different angles which allow light to enter and reflect back from the stone.
Refers to a girdle on which small facets have been polished to improve the brilliance of the diamond.
Viewing a diamond looking down onto the crown.
Part of the GIA colour grading scale that contain the colour grades K, L and M.
Diamonds with natural colours outside the normal market range are classified as fancy colour diamonds.The colour is described in terms of their hue, tone, and saturation. The colour characteristic plays the most important role in the value of a fancy coloured diamond.
One of the 6 grades on the GIA colour grading scale for fancy coloured diamonds.
Any style of diamond shape other than the round brilliant is called a fancy shape.
A feather is a general term for any type of fissure inclusion within a diamond. Another term for a crack.
A term to represent the combined quality of the surface condition (Polish) of the diamond as well as the size, shape and placement of the facets including the evenness of the outline (Symmetry).
Fire is not the same as dispersion. These two terms refer to different, but related, attributes. Fire is the appearance of coloured flashes. Fire varies from diamond to diamond, and is influenced by a diamond’s proportions as well as different lighting conditions and viewing environments.
Fisheye is an undesirable effect that happens when the viewer can see the reflection of the girdle through the table without tilting the diamond. A fisheye appears when the diamonds pavilion is too shallow or the table is too large, or as a combination of the two.
A clarity grade. No inclusions or blemishes are visible to a skilled grader using 10× magnification.
Fluorescence is the visible light that some diamonds emit when exposed to ultraviolet (UV) rays.
A universal grading system for comparing diamond quality based on colour, clarity, carat weight and clarity.
A rough diamond with high enough quality to be considered for polishing and use for jewellery wear.
GIA – Gemmological Institute of America
Diamond grading laboratory.
The girdle is a narrow section of the diamond separating the crown from the pavilion and functions as the diamond’s setting edge.
A process where industry experts rate or grade diamonds based on the Four C's: cut, clarity, colour and carat weight.
A place that provides unbiased analysis of gemstone quality.
Graining / Internal Graining
A clarity characteristic. Caused by irregular crystal growth; may appear like faint lines or streaks agains a transparent background, or may appear milky, coloured or reflective. As with any clarity characteristic, the effect such graining has on the overall grade rests with five standard factors: Size, nature, number, relief, and location.
The Mohs scale of mineral hardness characterises the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. Diamond is the hardest natural mineral found on this planet. Don't confuse hardness with toughness. Toughness of a substance means its ability to resist fracture or breakage when it is stressed or impacted. So, while diamond is the ‘hardest’ substance, in terms of 'toughness' it can be only moderately rated. This is because of its ability to fracture along cleavage plane.
Hearts & Arrows
Diamonds that are cut to very narrow proportions that display a repeatable pattern of eight symmetrical 'arrows' in the face up position and eight symmetrical 'hearts' when viewed in the table down position.
A note of caution:
GIA & AGS do not recognise hearts and arrows as a component of cut grade. This is partly due to the fact that the presence of the pattern is not a guarantee of cut. Occasionally you will see a hearts and arrows notation on a GIA certificate. This is simply GIA noting that an H&A inscription is present on the girdle of the diamond. This is provided as information only, not as a confirmation of the presence or quality of any hearts and arrows pattern in the diamond itself.
A variation of a round stone. A 'V' shaped groove is made in the edge of the stone to give the heart shaped appearance. The width is approximately equal to the length.
HRD - Hoge Raad voor Diamant
Diamond grading laboratory
The basic colour of an object.
High Pressure High Temperature: a process to create and treat synthetic diamonds.
Form of round brilliant professing to have ideal proportions.
IGI International Gemmological Institute
Diamond grading laboratory.
Included (I1, I2, and I3)
Inclusions are obvious under 10× magnification and may affect transparency and brilliance.
A term for a clarity characteristic enclosed in a polished gemstone or extending into it from the surface.
A natural that penetrates the surface of the stone.
Internally Flawless (IF)
No inclusions and only blemishes are visible to a skilled grader using 10× magnification
A unit of measure for the fineness of gold.
An igneous rock that is sometimes diamondiferous. Kimberlite occurs in the earth’s crust in vertical structures known as kimberlite pipes.
Intergovernmental rough diamond certification scheme aimed at preventing conflict diamonds entering the legitimate diamond value chain.
An included diamond crystal within the main diamond that extends to the surface after polishing.
Lab Grown Diamond
The only difference between a Lab-Grown Diamond and a Natural Mined Diamond is its origin. A created diamond is ‘grown’ using technology that replicates a natural diamonds formation process (HTHP or CVD). This results in a man-made diamond that is chemically, physically, and optically the same as one which formed beneath the Earth.
Laser drilling is the process of drilling a hole with a laser beam from a point on the surface of a diamond to a dark inclusion trapped within the diamond. The beam vaporises a tiny channel, or ‘drill hole’, to the dark inclusion; this provides a conduit to the inclusion from the surface, and then boiling the diamond in acid will remove the dark inclusion or cause it to be less visible. The drill holes themselves appear as fine, straight tunnels from the surface of the diamond to an inclusion. According to internationally accepted rules for diamond certification, laser drilled diamonds are allowed to be certified because the treatment is permanent – it will not change or revert back to its original state. However, the treatment must be clearly stated on the certificate. Laser drilling may improve the appearance of a diamond, but it also reduces its value.
Laser inscription is the laser etched text put on diamond girdle for identification. Usually the text is the grading laboratory initials and the certification number.
A comparison of the length and the width of a fancy shape diamond. This ratio expresses how relatively long or wide a diamond appears when viewed from the top. Each of the fancy shapes has a certain length-to-width ratio that is considered most appealing for that shape. However, personal preference prevails, and some may prefer a shorter wider outline or longer thinner shape. The length-to-width ratio is calculated by dividing the length of the diamond by its width.
Part of the GIA colour grading scale that contain the colour grades S, T, U, V, W, X, Y and Z.
When the light that enters through the crown of a diamond escapes out the sides or bottom, rather than returning to the viewers eye through the crown. This results in the diamond losing some brilliance or appearing dark or dull in some areas.
A polished diamond that is not yet fixed in a setting as a finished piece of jewellery.
A magnifying lens set at 10X magnification and corrected for colour. This is the industry standard for viewing diamonds.
A diamond industry trade term. Used if, after an examination by an experienced grader with a loupe at 10X magnification (corrected for spherical and chromatic aberration), it has been found free of internal characteristics.
The quality of the work in fashioning the shape. Refers to how well a diamond is cut and faceted to bring out the full beauty of the rough crystal.
A type of fancy shape, brilliant cut diamond forming an elongated oval with points at each end.
A term used to describe small cut and polished diamonds. The diamond weight for melée diamonds ranges from as low as 0.001 carats (1,000th/carat) to 0.18 carats.
Mixed cuts share aspects of both modified brilliant and step cuts. Typically, the crown is brilliant cut and the pavilion step cut. Mixed cut examples include the princess and radiant shapes.
Modified Brilliant Cut
Many popular fancy shapes have adopted this faceting style because the standard round brilliant can be effectively modified into a wide range of shapes. Because their facet counts and facet arrangements are similar, modified brilliants also look, in terms of brilliance and fire interplay, the most like round brilliants and are therefore, in general, the most saleable. Modified brilliants include the marquise, heart, triangular, trilliant, oval, and pear.
A hardness scale developed in 1822 by Austrian Friedreich Mohs as a criterion for mineral identification. The scale ranks 0-10 for hardness. Harder minerals, with a higher number, can scratch those with a lower number. A diamond, ranked at ten, is 58 times harder than the next hardest mineral on earth, corundum, from which rubies and sapphires are formed, ranked at 9.
Moissanite is a lab created stone based on the structure of natural moissanite. It displays similar properties to diamond and is often used as a diamond simulant. On the Mohs' scale of hardness, moissanite is 9.5.
A portion of the original surface of the rough diamond which has been left on a polished diamond.
A diamond formed naturally over millions of years in the earth’s crust. Diamonds that have not been treated or enhanced.
Part of the GIA colour grading scale that contain the colour grades G, H, I and J.
Fluorescence can occur in different intensities. Gemological laboratories rate the fluorescence of each diamond on a scale from "None" to "Very Strong".
When an inclusion within a diamond reaches the surface. If there is a feather, chip, cavity, pit or natural breaking a surface facet, then such inclusions are referred to as ‘opens'.
A fancy shape modification of the round brilliant cut. The oval cut diamond is comparable to a brilliant cut with an oval shape.
A lightweight, hypoallergenic metal used as an alloy in jewellery.
A way of setting diamonds, where they are placed together so closely, that no metal shows.
The portion of a diamond below the girdle.
The angle measured between the table and the pavilion main facet.
Average pavilion depth relative to the average diameter, reported to the nearest half of a percentage point. Pavilion depth is measured from the culet to the intersection of the pavilion main facet with the girdle.
Pavilion Main Facet
The eight facets found on the pavilion of a round brilliant diamond. Their points touch the girdle.
Pink Champagne Diamonds
Developed by Argyle Pink Diamonds, this is one of the colour grades for classifying pink diamonds. A Pink champagne diamond is a diamond with primarily a champagne hue (light brown), with pink also present in the hue.
A brilliant cut diamond with a pear shaped outline having two curved sides, one rounded end and one pointed end.
An exceedingly rare colour of diamond. Exactly what gives a pink diamond its colour is largely unknown, and the subject of ongoing debate. It's thought that they obtain their pink colour as a result of the structure being altered.
Formerly known as Brownish Pink (BP). Developed by Argyle Pink Diamonds, this is one of the colour grades for classifying pink diamonds. A diamond with a primary pink hue with light brown light brown present in the hue.
Very small inclusions in a diamond.
Piqué is a European term for imperfect. It is an old trade term for diamond clarity. Piqué 1, 2 & 3 correspond to the GIA clarity grades I1, I2 & I3.
A map of a diamond's interior and exterior clarity characteristics that have set the clarity grade. A diamond plot is a graphic representation of inclusions and blemishes that affect the overall clarity grade. Besides the plot, there is also a comment section on the certificate where additional clarity characteristics are often noted. These are usually too minor to be reflected in the plot itself.
A diamond plot does not reproduce the actual appearance of a diamond. Often, a plot may carry only one or two markings, as this may be all that was required for the setting the clarity grade it received.
One hundredth (1/100th) of a carat (.01ct). Example, a 1/2 carat diamond weighs 50 points.
Refers to how smooth the facets of a diamond have been polished. Diamonds that have a poor polish are less brilliant because they have polish lines that blur the surface of the diamond and can reduce the amount of light that enters or exits a diamond.
see Faceted Girdle
Price Per Carat
Diamonds are priced according to carat weight. For example, if you have a diamond with a carat weight of 1.31cts and a per carat price of $9187.00, you would simply multiply 1.31x9187=$12,035 for the diamond.
A fancy shape, mixed cut with a square or rectangular face up outline. The 2nd most popular diamond shape after the round brilliant.
The relative dimensions and angles of a diamond’s faceting and the relationships that exist between them. Used to determine the cut grade for round brilliants.
Developed by Argyle Pink Diamonds, this is one of the colour grades for classifying pink diamonds. For stones with a colour grade of purplish pink (PP), the predominate colour is pink with a slight under-hue of purple.
A loosely used term referring to the overall grading results of the 4Cs.
A fancy shape diamond. The radiant cut diamond combines the brilliance of the standard round brilliant cut diamond with the emerald cut diamond shape. A radiant can also be square.
Rapaport Diamond Report
Monthly wholesale diamond price list used by dealers worldwide to keep up with changing market prices.
See Length-to-Width Ratio
Because the natural colour of white gold is actually a light grey colour, most white gold jewellery is plated with a hard, white metal known as rhodium. Rhodium is what gives white gold its impressive silver shine. The rhodium is very hard, but eventually it will wear away, especially with hand worn jewellery. Therefore, a white gold ring will likely have to be re-rhodium plated every 1-2 years. Most jewellers are able to reapply the rhodium plating on jewellery for a relatively low cost.
An uncut, unpolished diamond.
The most common and popular cut, usually containing 57 facets. Also the most brilliant cut, in terms of the most efficient use of light to increase brilliance and fire.
Refers to how vivid and intense a colour is. For example, a diamond with poor colour saturation will look washed out or faded.
Flashes of light reflected from the crown.
The metal mounting and surround of a diamond when in a piece of jewellery.
Refers to the basic form or face up outline of a polished diamond. Examples are Round, Princess, Emerald, Radiant, Cushion, etc.
see Slightly Included
Accompanying stones that frame a larger centre diamond. Side stones can have different shapes, and the shape is chosen to compliment the shape of the centre stone.
A substance used to imitate diamond.
Round shape with an octagonal shaped table and eight facets on each the crown and pavilion. This cut eventually evolved into the brilliant cut with the complete rounding of the girdle and the application of additional facets to the crown and pavilion. Usually in pavé settings or in cases when many small diamonds are set together.
Slightly Included (SI1 and SI2)
Inclusions are noticeable to a skilled grader using 10× magnification. SI3 is a clarity grade commonly used within the diamond trade, but not recognised by certificate laboratories.
A ring set with a single diamond.
The process of classifying diamonds into a variety of categories based on their natural characteristics, specifically their colour, clarity, carat and model or shape.
Spread / Spready
Spread refers to an expected millimetre size in relation to the carat weight. For example, a 1ct round brilliant would have an expected diameter (spread) of approximately 6.45mm.
Spready is a term that is used frequently in the diamond trade to refer to a stone that has been cut with a large table and a thin crown and girdle to make it appear bigger than it actually weighs. Example, a 1ct round brilliant has been cut shallow to give it a diameter of 6.6mm. This gives the appearance that the diamond is the same weight as a 1.10ct stone.
A cutting style in which narrow, rectangular facets are arranged in rows parallel to the girdle on both the crown and pavilion.
Refers to the exactness of the shape of a diamond and the symmetrical arrangement and even placement of the facets.
A man-made diamond with the same chemical composition, crystal structure and physical properties as its natural counterpart. Where a product is man-made, but has the same structure as a natural counterpart, an accepted description must be used to make clear that the product is man-made. Synthetic is one such description.
The large facet in the centre of the crown of a polished diamond.
An industry trade term referring to a diamond with no eye visible inclusions directly under the table.
The average table size relative to the average diameter, reported as a percentage. Table size is measured from bezel point to bezel point with the average of four measurements used.
A tapered modification of the straight baguette, with one end cut narrower than the opposite end. Usually used as side stones.
The lightness or darkness of the colour in a diamond.
A measure of cut. Total depth (measured from table facet to the culet) relative to the average diameter reported as a percentage.
Any non-natural processes (other than shaping, polishing and surface cleaning) that change, interfere with and/or contaminate the natural appearance, composition or durability of a gemstone. For diamonds, this includes colour treatments (and decolourisation or ‘bleaching’), fracture filling, laser-drilling, irradiation treatment, and coating.
Trilliant / Trillion Shape
A type of fancy shape triangular diamond. Trilliant cut diamonds have the sharp corners of a true triangle, while trillions have slightly rounded corners.
A type of clarity inclusion. Produced by crystal distortion within the diamond. Might look like a light coloured twisting ribbon within a stone.
A synthetic diamond that has been falsely passed off as a natural gem.
Upper Girdle Facet
In a round brilliant diamond, they are the 16 facets that go around the perimeter of the diamond and meet the star facets at their point.
A valuation attempts to issue a dollar value to replace your diamond jewellery with similar items for the purpose of insurance. Not to be confused with a diamond certificate.
Very Light Colour
Part of the GIA colour grading scale that contain the colour grades N, O, P, Q and R.
Very Slightly Included (VS1 and VS2)
Inclusions are clearly visible under 10× magnification but can be characterised as minor
Very, Very Slightly Included (VVS1 and VVS2)
Inclusions are difficult for a skilled grader to see under 10× magnification.
An alloy of gold and at least one white metal to lighten its colour and add strength and durability.
Very small facets polished on to the rough diamond to see more clearly into the stone.
The weight of a polished stone achieved from the rough normally expressed as a percentage.
Yellow diamonds are considered to be a coloured diamond and graded as “Fancy” when they fall outside the D-to-Z range (colourless to light-yellow). A Fancy grade means that the yellow diamond must have more colour than the Z master-stone. The GIA Coloured Diamond Grading System assigns yellow diamonds one of six colour grades: Fancy Light, Fancy, Fancy Dark, Fancy Deep, Fancy Intense, and Fancy Vivid.