Glossary

A

Abrasion
Referring to a diamond’s clarity, an abrasion is a series of tiny nicks along facet junctions, producing white fuzzy lines instead of sharp crisp facet edges.

Asscher cut
A fancy shape diamond cut with straight, step-like facets resembling the Emerald cut diamond but it is square in shape with the corners cut off. Also known as a Square Emerald Cut.

B

Baguette
A fancy shape diamond cut with step-cut facets and is rectangular in shape.

Bearded girdle
Tiny, numerous, hair-like fractures extending from the girdle into the diamond.

Bezel facet
On a round brilliant diamond, these are eight large kite-shaped facets on the crown, also called top main facet.

Blemish
A blemish refers to damage that occurs on the surface of a diamond and effects a diamond's clarity grading. E.g. a nick, knot, scratch, abrasion, minor crack or fissure (cavity), or a poor polish.

Bow tie effect
A bow tie is caused by an area of shadow visible in fancy diamond shapes, usually due to light leaking from the bottom of the diamond.

Brilliance
Brilliance describes the amount of white light reflected from the facets of a diamond.  Brilliance is a combination of lustre, light reflection, colour dispersion and scintillation.

Brilliant cut diamond
The Round Brilliant Cut diamond is the most common cut usually containing 57 facets (58 if the culet has been polished). Also the most brilliant cut, in terms of most efficient use of light to increase brilliance, fire and scintillation.

Bruise
Damage consisting of surface crumbling, often accompanied by tiny, root like feathers.

Burn mark / burned facet
Surface clouding caused by excessive heat.

C

Carat
Carat is one of the diamond grading 4Cs. The standard unit of measurement referring to the weight of a diamond. One carat is equivalent to 200 milligrams, or one-fifth of a gram.

Cavaity
A type of inclusion consisting of a large or deep opening in the diamond.

Certified diamond  
A diamond that has been sent to a independent diamond grading laboratory such as the GIA - Gemological Institute of America. Such a diamond will always be sold with its unique diamond grading report

Clarity
Refers to the incidence of inclusions (internal imperfections) and blemishes (external imperfections). Clarity is graded on a scale from Flawless (F) to Imperfect (I), and the size, number, position, nature and colour of these imperfections determine the clarity grade and greatly affect the value the diamond.

Claws
The metal that holds a diamond or gemstone in place. Also known as prongs.

Cleavage
The tendency of a crystalline mineral to break in certain definite directions called cleavage planes. A cleavage may be caused by inherent internal strain or by a sharp blow. The break may extend to the surface of a diamond.

Cloud
A group of minute white inclusions too small to be distinguishable from another that gives a cloudy or milky appearance inside the diamond.

Colour
Grading the colour of a diamond involves deciding how closely a diamond's colour appears to be colourlessness. The colour of a diamond is ranked on a scale from ‘D' to ‘Z', where ‘D' is colourless and ‘Z' has a noticeable tint of colour, typically yellow. Most diamonds have a trace of yellow or brown. With the exception of some natural fancy colours, such as blue, pink, purple, or red, the colourless grade is the most rare and hence the most valuable.

Crown
The upper part of the diamond just above the girdle. It consists of a large flat area on the top of the diamond known as the table, and several crown facets below it.

Crown angle
The angle measured between the girdle plane and the bezel facets. Along with the table size, the crown angle helps determine the amount of dispersion displayed by the diamond.

Crown height
The part of the diamond that is above the girdle.

Crystal
A type of inclusion. A crystal is a mineral deposit trapped inside the diamond, and can vary in colour.

Cutlet
The smallest facet at the bottom of a full-cut diamond, resembling a sharp point or tip at the bottom of the pavilion on a faceted diamond. When the culet is polished, it adds an extra facet to the diamond, i.e.: a normal round brilliant cut diamond has 57 facets if the culet is not polished and 58 facets if the culet is polished.

Cushion cut
A fancy shape diamond cut with rounded edges and sides, no sharp points. The shape of the cushion cut resembles a pillow or cushion, hence its name.

Cut
The cut of a diamond refers to the proportions given to the polished diamond by the diamond cutter. Proportions are the size and angle relationships between the facets and different parts of the diamond. Cut affects both the weight yield from a rough diamond and the optical efficiency of the polished diamond. It is the most important of the 4Cs in determining the diamond's overall fire, brilliance and scintillation.

 

D

Depth
The distance between the table (top) and the culet (bottom) of a diamond or gemstone as measured in millimetres.

Diamond grading report
A formal document detailing a diamond’s unique characteristics, especially it’s cut, carat weight, colour and clarity, and may also include its finish (polish and symmetry), fluorescence and additional comments.  A diamond grading report is issued by an independent laboratory such as the GIA - Gemological Institute of America. These reports are numbered and are unique to each and every diamond graded.

Dispersion
The display of spectral colours emanating from a diamond as white light is broken-up when it enters the diamond.

E

EGL
European Gemmological Laboratory (EGL) is an independent international diamond grading laboratory responsible for certifying diamonds based on the 4Cs (cut, colour, clarity and carat weight).

Emerald cut  
A fancy diamond shape that has a step cut and is usually rectangular in shape with cut corners.

Excellent cut
Refers to the proportions of a diamond’s cut. If ideal proportions and symmetry is achieved, the diamond cut will be graded as excellent meaning that there is maximum fire, brilliance and scintillation.

Eye-clean
In clarity grading, an eye-clean diamond has no inclusions that are visible to the naked eye. In other words, the diamond will appear flawless to the naked eye. Diamonds that generally have a clarity higher than SI1 will appear to be eye-clean from inclusions.

F

Facet
The polished planes on the surface of a diamond that gives the finished diamond its shape. The degree and amount of light that reflects from these facets gives a diamond its brilliance and sparkle.

Faceted diamond
A diamond that has transformed from rough into a polished stone with all of its facets.

Fancy shape diamond / fancy cuts
Diamonds that are cut into any shape, other than round, are considered fancy shaped diamonds and typically have a lower cost per carat. Examples of fancy shape diamonds are Princess, Emerald, Asscher, Cushion, Radiant, Oval, Pear, Marquise, Heart etc.

Feather
A type of inclusion or break in a diamond that looks like a white feather. The presence of a feather is noted in the clarity grade of a diamond.

Finish
Also known as the polish and symmetry of the diamond. The finish refers to exterior of the diamond.

Fire
Fire refers to flashes of light seen from within a diamond resulting from dispersion. Diamonds that are cut to very good or excellent proportions will display a higher degree of fire.

Flaw
An imperfection within a diamond. Flaws are noted in the clarity grade.

Fluorescence
The degree of luminescence exhibited in certain diamonds when exposed to ultraviolet light or strong sunlight. Most commonly, diamonds fluoresce blue in colour, but can also be a variety of other colours.

Fracture
A crack or break on a diamonds surface.

G

GIA
Gemological Institute of America (GIA) is a well respected independent, international grading laboratory responsible for the grading of diamonds. Many of the world’s most precious diamonds and gemstones are graded by the GIA. 

Girdle
The narrow band around the widest part of the diamond or gemstone. The girdle can be faceted, polished or unpolished.

Girdle thickness
The measurement describing the percentage of the diamond's average girdle diameter. The descriptions of girdle thickness range from extremely thin, thin, medium, slightly thick, thick and extremely thick.

Grading report
See Diamond grading report.

Gold
A precious metal widely used in the jewellery trade. Gold has the longest and most storied history of all precious metals. Gold in jewellery terms is expressed in karats (abbreviated in K or KT). Pure gold is 24K and is very soft in nature. 18K gold contains 75% gold and 25% other metals to make it stronger and more suitable for every day wear in jewellery.

H

Hardness
Refers to a diamond or gemstone’s resistance to scratching. A diamond is the hardest mineral known to man.

Hearts and Arrows
A general term used when referring to diamonds with a precise and complete pattern of hearts and arrows achieved by perfect proportions and symmetry in a diamond’s cut. When viewing a diamond from the top, it shows an arrows pattern and when viewed from the bottom you’ll see a series of hearts. A true Hearts and Arrows diamond must have all patterns visible at a single glance; this indicates the diamond has optically perfect symmetrical.

Heart shape
A type of fancy cut diamond that resembles the shape of a heart.

I

Ideal cut
Generally used to describe a round brilliant cut that is cut to perfect proportions and symmetry.

Inclusion
A natural imperfection in a diamond which affects the clarity grade of the stone. Examples of inclusions found in diamonds are feathers, crystals, needles, clouds and pinpoints.

Internal graining
Indications of irregular crystal growth within a diamond or gemstone. These may appear milky, similar to faint lines or streaks, or may have colour or be reflective.

L

Length to width ratio  
A comparison of the length and width of the girdle outline on fancy shape diamonds. The ratio is found by dividing the length of the diamond by the width. The width is always stated as 1. Some length to width ratios are considered to be more appealing than others, but this is a matter of personal preference.
Pear 1.50 - 1.75 : 1
Marquise 1.75 - 2.25 : 1
Heart 0.98 - 1.02 : 1
Oval 1.33 - 1.66 : 1
Emerald 1.50 - 1.75 : 1
Radiant/Princess 0.95 - 1.05 : 1

Light leakage
The amount of light lost through a diamond when it has not been cut to perfect proportion and symmetry. If the diamond cut is too shallow or too deep, light that is refracted within the stone will seep through the sides resulting in a loss of brilliance and sparkle. Diamonds with a zero light leakage such as the Brilliant 10, will display a higher degree of fire, brilliance and scintillation. In effect, this means that light that enters the diamond will be refracted within the stone and then reflected back through the top again.

Loupe
A small magnifying lens used to examine diamonds. 10x magnification is the standard measurement tool for determining the clarity of a diamond.

Lower-girdle facet
The facets on the pavilion of a round brilliant cut found just below the girdle.

M

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

Melee
A term used primarily to describe small, round faceted diamonds of approximately .18 carat or less.

Mount
An item of jewellery which is ready to have the centre / main diamond or gemstone set into.

Mine cut diamond
An early form of the brilliant diamond with a squarish-shaped girdle, high crown, small table, deep pavilion, and very large culet.

Mohs Scale of Hardness
The 10-point scale of mineral hardness. On the Mohs scale of relative hardness, a diamond is rated as 10 meaning that it is the hardest mineral known to man. Only a mineral of the same hardness grade can scratch the mineral. Sapphires for example are graded as 9 on the Mohs scale of hardness which means that only another Sapphire or a diamond (because a diamond is harder) can scratch a Sapphire. Yet, Sapphires cannot scratch a diamond because they are softer.

Mohs 10-point scale of mineral hardness table.

 Hardness (from hard to soft)  Mineral
 10  Diamond
 9  Corundum, Sapphire and Ruby
 8  Emerald, Aquamarine, Topaz, Beryl and Hardened Steel
 7  Quartz, Amethyst, Citrine and Agate
 6.5  Tanzanite, Steel file, Iron Pyrite, Glass and Vitreous Pure Silica
 6  Orthoclase, Titanium and Spectrolite
 5  Apatite
 4.5  Platinum and Iron
 4  Fluorite
 3  Calcite and Copper Coin
 2.5  Pure 24K Gold, Silver and  Aluminium
 2  Gypsum
 1  Talc
N

Natural
Refers to blemishes that can be found on some polished diamonds when some of the rough is left on the diamond.

Needle
A long, thin included crystal that looks like a tiny rod. The incidence of a needle will affect the clarity grading of a diamond.

O

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

P

Pave
A pave or pavé (pronounced pah-vay) setting is a diamond or gemstone setting in which multiple small stones are set close together and very close to the surface of a piece of jewellery, making it look like as though the jewellery has been paved in gemstones.

Pavilion
The area of the diamond below the girdle measuring to the culet.

Pavilion angle
The angle measured between the girdle and the pavilion main facet.

Pavilion main facet
The eight facets found on the pavilion of a round brilliant diamond.

Pear shape
A type of fancy shape diamond that resembles a teardrop. One edge is rounded, much like an Oval Shape and the opposite edge has a sharp point, much like a Marquise Shape.

Pinpoints
Very small inclusions in a diamond that affect the clarity grade. A cluster of pinpoints can form a cloud.

Platinum
A precious metal that is more rare, more pure and stronger than gold.

Points
A measurement in the weight of a diamond equal to 1/100 of a carat. For example, a 0.20ct is equal to 20 points.

Polish
The way the cutter finishes the facets on a diamond. Laboratories grade polish from excellent to poor.

Princess cut
A type of fancy shape diamond that is square in shape with four pointed corners.

Proportions
The term 'proportion' refers to the relationship between the angles of the facets of the crown and pavilion polished on a diamond or gemstone. Obtaining perfect proportion is very important in order to maximise fire, brilliance and scintillation so that the right amount is light enters the stone, is refracted within the stone and reflected back through the top of the stone.

Prongs
The metal that holds a diamond or gemstone in place. Also known as claws. Typical settings feature 4 or 6 claws or prongs.

R

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

Refraction
The change in direction of a ray of light as it enters the diamond or gemstone and is bounced from facet to facet.

Rhodium plating
White gold is typically rhodium plated when sold so that it resembles the white colour of platinum. With prolonged wear and acidic levels in skin, white gold may lose its rhodium plating and look slightly yellow in colour.

Rough
Refers to a diamond as it comes out of ground before it is cut and polished.

Rough girdle
A grainy or pitted girdle surface, often with nicks.

Round brilliant cut
See Brilliant Cut Diamond.

S

Scintillation
The amount of reflected light from a diamond visible when it moves. Also known as sparkle. 

Shape
Commonly mistaken for cut in the 4C’s but not the same. Cut refers to the finish (proportions and symmetry of a diamond or gemstone), while shape refers to its actual shape whether it is round, square, princess, radiant, cushion, emerald, square emerald, marquise, pear, oval or heart.

Square emerald
See Accsher Cut.

Star facet
One of the eight triangular facets found on the upper crown section, next to the table, of a round brilliant cut diamond.

Symmetry
The overall uniformity to the arrangement of the facets and polished angles of a diamond or gemstone, created when transforming a diamond from its rough state to a polished stone. Symmetrical grading ranges from excellent to poor. Excellent symmetry of a well gut and well proportioned diamond or gemstone will display a higher degree of fire, brilliance and scintillation. While poor symmetry will result in a loss of light and sparkle performance.

T

Table
The largest facet which is polished on the top of a diamond or gemstone. This horizontal facet is where most of the light enters and exits a diamond.

Table percentage
The width of the table divided by the average diameter. If the table facet is too large or too small, it will often indicate poor proportions overall.

U

Upper girdle facet
One of the 15 facets found on the lower crown portion of the diamond, just above the girdle.

V

Valuation certificate
A written estimate of the approximate retail replacement value of the item described. A valuation certificate can be used for insurance purposes and should be updated every two years to keep the value current. Also known as an appraisal.

W

White gold
A precious metal that is made up of gold, which in its natural form is yellow in colour, and is alloyed with other metals such as iridium and palladium. The finished product is then rhodium plated to make it look as close to platinum as possible.