• Appraisal

    A written estimate of the approximate retail replacement value of the item described. They can be used for insurance purposes and should be updated every few years.
  • Bezel Facet

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

    A quantitative measure of the amount of light return through the gem. A GIA Standardized term.
  • Brilliant Cut Diamond

    Round diamond with 57 facets (58 if there is a culet). Round brilliant cut diamonds are more brilliant than any of the fancy-shaped stones.
  • Carat

    The standard unit of measurement of the weight of a diamond. One carat equals 1/5 of a gram or 1/142 of an ounce. 1 carat=100 points.
  • Cavity

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

    The degree to which a diamond is free from blemishes / inclusions. Clarity is graded on a scale from Flawless (FL) to Imperfect.
  • Clarity Enhancement

    Any process used to improve the apparent clarity of a diamond. This may include filling fractures and cavities with glass/resin.
  • Cleavage

    A break in a diamond which is parallel to one of its crystallographic 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 tiny, white inclusions which give a cloudy appearance.
  • Color Grading

    A system of grading diamond colors based on their colorlessness (for white diamonds) or their spectral hue, depth of color and purity of color (for fancy color diamonds). For white diamonds, IGI uses the internationally recognized grading system which runs from D (totally colorless) to Z (light yellow).
  • Crown

    The part of the diamond that is above the girdle. It consists of the table and the 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 Percentage

    The crown height expressed as a percentage of the average girdle diameter.
  • Crystal

    A type of inclusion. A crystal is a mineral deposit trapped inside the diamond.
  • Culet

    The smallest (58th) facet at the bottom of a full-cut diamond. Some diamonds do not have a culet (none or pointed is how the culet of that diamond will be described).
  • Cushion Cut

    An antique style of cut that looks like a mix between an Old Mine Cut (see Mine Cut Diamond) and a modern oval cut.
  • Cut

    The cut (make) of a diamond refers to the proportions given to the polished diamond by the diamond cutter. The cut is the most important of the 4Cs (cut, color, clarity, carat) in determining the diamond's overall beauty.
  • Depth

    The distance between the table and the culet as measured in millimeters.
  • Depth Percentage

    The depth of the diamond divided by the average width.
  • Durability

    This covers thin girdles as well as inclusions that weaken a gem.
  • Emerald Cut

    A square or rectangular-shaped diamond with cut corners. On the crown, there are three parallel rows of facets arranged around the table and, on the pavilion, there are three parallel rows arranged around the culet. This type of cut is also known as a Step Cut because its broad, flat planes resemble stair steps. Inclusions that are visible through the table to the unaided eye.
  • Eye-Clean

    In clarity-grading, eye-clean diamonds should have no inclusions that are visible through the table to the unaided eye.
  • Facet

    A polished plane on the surface of a gemstone.
  • Fancy Color

    Diamonds having color more intense than "Z", as well as diamonds exhibiting color other than yellow or brown are considered fancy colored diamonds. These diamonds are graded using separate systems which indicate the characteristics of the color, and not just its presence.
  • Fancy Shape

    Any diamond shape other than round.
  • Feather

    A fracture or break in a diamond that looks like a white feather.
  • Fluorescence

    The property in approximately 50% of all diamonds that makes them glow when exposed to ultraviolet light (such as the lighting frequently seen in night clubs). Diamonds can fluoresce in a number of colors, but blue fluorescence is most common. Depending on its intensity, blue fluorescence may enhance the color of some diamonds by hiding their yellow tint.
  • Fracture

    A chip or break on a diamond that is not in the direction of a cleavage plane
  • Fracture Filling

    A treatment whereby feathers in a diamond are filled with an artificial substance. This treatment is not permanent since the filler can dissolve and escape over time.
  • Girdle

    The outer edge, or outline, of the diamond's shape. This is the area where the average diameter, width and length of stones are measured. The girdle is situated in-between the pavilion (lower part) and the crown (upper part). It can be faceted, polished or unpolished in which case it looks granular.
  • Girdle Thickness

    The measurement describing the girdle thickness is the average distance between the pavilion (lower part) and crown (upper part), measured in millimeters but usually expressed in percentage of the average diameter.
  • Hearts & Arrows (Pattern)

    "Hearts & Arrows" are usually (but not necessarily) Excellent-Ideal cuts of superior quality. Polishers used "secret recipes" to create the pattern of "Hearts" looking down through the pavilion and "Arrows" seen in the table-up position. The precision and sharpness of the patterns relied on precise angles in combination with specific facet length, width and azimuth.
  • Ideal Cut

    A diamond polished to the highest standards in precision and perfection, resulting in ideal balance between brilliance and 'fire'. The combination of angles and proportions, as well as the highest quality of polish and symmetry ensure optimal return of light.
  • GIL

    Gemological International Laboratories is one of a very small number of internationally recognized laboratories issuing diamond grading reports, colored stones reports, as well as fine jewelry reports.
  • Inclusion

    A naturally occurring imperfection in a diamond, commonly referred to as "internal characteristic". Some examples are: feathers, crystals, needles, clouds and pinpoints.
  • Karat

    Karat is the measure of purity of gold; 24-karat being pure gold. Jewelry is usually made from 18K and 14K gold, which contain other metals for strength.
  • Laser Drilling

    A diamond enhancement technique whereby a laser is used to drill to a dark inclusion which is then bleached in order to enhance the inclusion’s appearance.
  • Laser Drill Hole

    A tiny tube created during the laser drilling process of a diamond.
  • Laser Inscription

    Is the laser-etched text put on the girdle of a diamond for identification purposes. Usually the text is the laboratory initials (IGI) and the grading report number.
  • Length-To-Width Ratio

    A comparison of how much longer a diamond is than it is wide. It is used to analyze the outline of fancy shapes only; it is never applied to round diamonds. There's really no such thing as an 'ideal' ratio; it's simply a matter of personal preferences. For example, some people prefer the look of a long, slender marquise and others prefer the look of a shorter, fatter marquise. And while many people like square princess cuts and radiants, there are some people who enjoy more rectangular proportions for these types of fancy shapes.
  • Loupe

    A 10x magnifying lens used to examine diamonds and other gemstones.
  • Lower-Girdle Facet

    Also called "lower halves", they are the facets on the pavilion of a round brilliant just below the girdle.
  • Luster

    The degree to which a diamond or gemstone reflects light.
  • Marquise Cut

    An elongated shape with pointed ends inspired by the fascinating smile of the Marquise de Pompadour and commissioned by the Sun King, Louis XIV of France, who wanted a diamond to match it.
  • Mine Cut Diamond

    An ancient form of the brilliant diamond with a cushion-shaped outline, high crown, small table, deep pavilion, and an extremely large faceted culet
  • Mohs Scale

    The 10-point scale of mineral hardness created in 1812 by the German mineralogist Friedrich Mohs. It is one of several definitions of hardness in materials science. Diamond scores 10 on the Mohs Scale, 9 for Corundum (Ruby and Sapphire), 7.5 to 8 for Beryl (emerald and aquamarine) and 7 for Quartz. Diamond is the hardest of all known natural substances.
  • Natural

    A small rough diamond portion that can be found on some polished diamonds. This is often done so the polisher can maximize weight yield of a diamond.
  • Old European Cut

    The earliest known form of brilliant cut diamond with a very small table and steep crown.
  • Optical Property

    A gem's intrinsic ability to interact with light. Some optical properties are color, dispersion and fluorescence.
  • Pavé

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

    The lower part of a polished diamond, usually cone-shaped.
  • 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. They run from the girdle to the culet.
  • Pear

    Combining the best of the oval and the marquise, it is shaped like a sparkling teardrop.
  • Pinpoint

    Internal characteristic: minute to very small, usually a whitish dot inside a diamond.
  • Points

    1/100th of a carat. For example, a 3/4 carat diamond weighs 75 points.
  • Polish

    The way polishers finish the smoothness of facets on a diamond. Polish is graded starting at "Excellent" and followed by "Very Good", "Good", "Fair" and "Poor".
  • Princess

    This is a square or rectangular cut with numerous sparkling facets.
  • Scintillation

    The small areas of light in a polished diamond that flash on and off as the diamond, observer or lighting moves.
  • Shape

    The shape of a gemstone. The most famous are known as round, marquise, pear, oval, heart, princess, radiant, emerald, cushion and triangle but there are also many other shapes.
  • Star Facet

    One of the eight triangular facets found at the edge of the table facet and pointing to the outline of a brilliant-cut diamond.
  • Step Cut

    A square or rectangular-shaped diamond with cut corners. On the crown, there are three parallel rows of facets arranged around the table and, on the pavilion, there are three parallel rows arranged around the culet. This type of cut is also known as a Step Cut because its broad, flat planes resemble stair steps. Inclusions that are visible through the table to the unaided eye.
  • Symmetry

    Symmetry of individual facets, and symmetry of the parts of the stone as well as their overall alignment, is what a gemologist must observe and grade from 'Excellent' to 'Poor'.
  • Table

    The largest facet, situated on top of the crown of a diamond. This is where most of the light enters and exits a diamond.
  • Table Percentage

    The width of the table divided by the average diameter.
  • Upper-Girdle Facet

    Also called "upper halves", they are the 16 facets found on the crown, between the girdle and the star facets.