AGS is the American Gem Society and is the recognized authority for grading gemstones in the jewelry industry. AGS has a cut grading system for round diamonds.
Alloy is a mixture of two or more metals.
Appraisal is a written estimate of the approximate retail replacement value of an item described. They can be used for insurance purposes and should be updated every few years.
|Asscher Cut |
Asscher Cut is the step cut diamond shape with cut-corners and square shape.
Baguette is a rectangular shape into which gemstones and diamonds are commonly cut. Baguettes are often used as side stones in ring mountings.
Bail is the attachment at the top of a pendant, enabling the pendant to hang from a chain.
|Bezel Facets |
Bezel Facets are kite-shaped facets on the crown of brilliant-cut diamonds. The star pavilion mains, and upper and lower girdle facets are other facets found on brilliant cuts.
Blemish is a flaw on the exterior of a diamond, such as a scratch, abrasion, nick or chip
Blue-white refers to a diamond that glows (fluoresces) blue under ultraviolet light
|Bow Tie |
Bow Tie is the dark shadow in poorly cut elongated diamonds that looks like a man's bow tie when particularly noticeable.
Brilliance refers to the amount of light reflected through the surface of a diamond and is maximized by cutting a diamond to the correct proportions.
|Brilliant Cut |
Brilliant Cut is the common style of diamond cutting. The standard brilliant cut consists of 32 facets plus a table above the girdle and 24 facets plus a culet below the girdle. Other shapes besides round can be faceted as brilliant cuts, including oval, radiant, pear or heart.
Carat is the unit of weight, equal to 200 milligrams. In ancient times one carat was equal to one carob bean or four grains of rice.
|Carbon Spots |
Carbon Spots are the name often used for black spots in diamonds. This is misleading since these spots are certainly not coal, but usually transparent diamond crystals within the main diamond.
Cavity is a type of inclusion consisting of a large or deep opening in the diamond.
Certification is a grading report that is given to a diamond (and sometimes a precious gemstone) by a reputable and recognized gemological laboratory that defines the physical characteristics and quality rating of a gem.
|Channel Set |
Channel Set is a style of setting used for diamond and gemstone jewelry, channel set gems rest in a metal channel, where each gem sits perfectly adjacent to the next in a line. Channel set gems are typically round, princess cut or baguette shaped.
Clarity, a measure of quality for gemstones, is graded based upon internal flaws or inclusions. Because diamonds are created by nature over millions of years of intense heat and pressure, imperfections or inclusions are often formed in the process.
|Clarity Enhancement |
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.
Cleavage is 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 are hazy or milky areas in a diamond. Most clouds are made up of crystals too tiny to see individually even under a 10X magnification.
Color is one of the Four C's of diamond quality rating. The term color actually refers to the absence of color in a diamond.
|Color Grading |
Color Grading is 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, GIA and AGS use a grading system which runs from D (totally colorless) to Z (light yellow).
|Colored or "Fancy"|
Colored or "Fancy" diamonds are those that are not white. Fancy diamonds can be found in a full spectrum of hues, which include: blue, brown, black, violet, pink, green, yellow and red.
Crown is the upper part of the diamond above the girdle. It consists of the table and the crown facets below it.
|Crown Angle |
Crown Angle is 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 |
Crown Height is the millimeter distance the table is above the girdle.
|Crown Height Percentage |
Crown Height Percentage is the crown height expressed as a percentage of the average girdle diameter.
Crystal is a type of inclusion where a mineral deposit is trapped inside the diamond.
|Cubic Zirconia |
Cubic Zirconia is a man made gem which mimics diamond, yet does not have the same intrinsic properties such as hardness. Through a process developed in 1977, "CZ's" as they are often called, are mass produced and much less expensive than diamonds.
Culet is the tiny facet on the pointed bottom of the pavilion, parallel to the table. Its purpose is to protect the tip of the pavilion from being chipped or damaged.
|Cushion Cut |
Cushion Cut is a gemstone that is cut to mimic a square, yet has rounded edges. The cut is usually brilliant to give the highest light refraction.
Cut refers to the geometric proportions of a gemstone. The cut of a gemstone is one of the most important factors in determining how much sparkle a gemstone produces.
Depth is the height of a gemstone measured from the culet to the table.
|Depth Percentage |
Depth Percentage is the height of a gemstone, measured from the culet to the table, divided by the width of the gemstone. The depth percentage is critical to creating brilliance and fire in a diamond. A gemstone with a depth percentage too low or too high will lack sparkle.
Diamond is a crystal made up of 99.95% pure carbon atoms arranged in an isometric, or cubic, crystal arrangement. It is this unique arrangement of the carbon atoms that makes diamond look and behave differently from other pure carbon minerals such as graphite (the soft black material used to make pencils).
|Diamond Cutting |
Diamond Cutting is the method by which a rough diamond that has been mined from the earth is shaped into a finished, faceted stone.
|Diamond Gauge |
Diamond Gauge is an instrument that is used to measure a diamond's length, width and depth in millimeters.
Dispersion is the colored light reflected from within a diamond; also called "fire."
EGL is the abbreviation for the European Gemological Laboratory that has franchises in a number of cities around the world and in the USA which grade diamonds and offer a diamond grading certificate.
|Emerald Cut |
Emerald Cut is a square or rectangular-shaped diamond with cut corners. On the crown, there are three concentric rows of facets arranged around the table and, on the pavilion, there are three concentric rows arranged around the culet. This type of cut is also known as a Step Cut because its broad, flat planes resemble stair steps.
Eye-Clean refers to a diamond that has no inclusions or blemishes visible to a naked eye.
Facet is the flat, polished surface on a diamond. A round, full-cut diamond usually has 58 facets.
|Fancy Shape |
Fancy Shape is any shape except rounds. A pear shape is an example of a fancy shape. Sometimes fancy shapes are simply called fancies.
Feathers are cracks of various sizes. Normally, these do not weaken the diamond and can be difficult to see if small and oriented vertically.
Finish is the term that 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. The execution of the diamond's design, the precision of its cutting details, and the quality of its polish are all a consideration when a gemologist is grading finish. If you examine a diamond's grading report, you will see its finish graded according to two separate categories: polish and symmetry.
Fire is the colored light reflected from within a diamond through the crown. Fire is maximized by cutting a diamond to the correct proportions.
Fluorescence is a diamond's reaction to ultraviolet (UV) light, causing the stone to glow in various colors.
Fracture is a crack or feather in a diamond or gemstone in the opposite direction of its naturally occurring crystals.
|Fracture Filling |
Fracture Filling is a diamond enhancement process whereby a cavity or fracture in a diamond is filled with an artificial substance.
GIA refers to the Gemological Institute of America, an independent, non-profit organization which sets and upholds standards for grading diamonds and other precious stones.
Girdle is the narrow rim around the diamond. The girdle plane is parallel to the table and is the largest diameter of any part of the stone.
|Girdle Thickness |
Girdle Thickness is the measurement describing the percentage of the diamond's average girdle diameter.
|Grading Report |
Grading Report is sometimes called a "certification," although laboratories do not "certify" diamonds. The grading report, issued by an independent laboratory, should accurately describe the proportions, weight, color, clarity, symmetry, polish and possible fluorescence seen in the diamond being evaluated.
Hardness is a stone's ability to resist scratching, surface inclusions, abrasions or cracking
Head is the part of a ring that contains the prongs which hold a diamond in its setting.
|Heart Cut |
Heart Cut is a diamond or gemstone cut in the shape of a heart.
|Hearts & Arrows |
Hearts & Arrows is a pattern that visible in round diamonds with exceptional symmetry when view through a hearts & arrows scope.
Hue is the term used for the actual color of the spectrum (red, orange, yellow, green, blue, indigo or violet). The more pure a gemstone's hue, the more valuable it is. Because gemstones are comprised of many naturally occurring elements, they typically emit one primary color and one or more underlying colors.
Inclusion is the trace minerals, fractures and other imperfections that contribute to the unique fingerprint of a gemstone. All but the rarest gemstones contain inclusions, which are created during the gemstones formation in the earth.
|Invisible Setting |
Invisible Setting is a style in which rows of square princess cut diamonds or gemstones rest perfectly flush against one another within a metal border, with no metal separating them.
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-Drilled is a diamond that has been treated with a laser to remove dark "carbon" spots.
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.
|Length-to-Width Ratio |
Length-to-Width Ratio is 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 aesthetic preferences.
Loupe is a small magnifying glass used to view gemstones.
|Lower-Girdle Facet |
Lower-Girdle Facet is the type of facet on the pavilion of a round brilliant just below the girdle.
Luster is the degree to which a diamond or gemstone reflects light.
|Marquise Cut |
Marquise Cut gemstone is brilliant cut, forming an elongated oval with pointed ends.
|Mine Cut Diamond |
Mine Cut Diamond is an early form of the brilliant diamond with a squarish-shaped girdle, high crown, small table, deep pavilion, and very large culet.
|Moh's scale |
Moh's scale was devised in 1812 by Austrian mineralogist, Friedrich Moh to measure a mineral's hardness and it's resistance to scratching. The scale goes from talc as number 1, being the softest, to diamonds as number 10, being the hardest substance known.
Mounting refers to an item of jewelry in which one or more stones are set.
Naturals are part of the original surface of the diamond crystal left unpolished.
Off-Make is a poorly proportioned diamond.
|Old European Cut |
Old European Cut is the earliest know form of a brilliant cut diamond with a very small table, heavy crown and large depth.
|Optical property |
Optical property is a gem's intrinsic ability to interact with light. Some optical properties are color, dispersion and fluorescence.
|Oval Cut |
Oval Cut is an elliptical shaped diamond or gemstone that is slightly oblong.
Pavé is 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.
Pave is a method of setting diamonds very closely together, giving the illusion of one or more larger diamonds.
Pavilion is the lower part of the diamond below the girdle. It's cone-shaped on a round diamond.
Pavilion Angle is the angle measured between the girdle and the pavilion main facets.
|Pear Cut diamond |
Pear Cut diamond or gemstone is shaped like a teardrop, rounded on one end and pointed on the other.
Pinpoints are very small inclusions, difficult to see at 10x magnification.
Platinum is one of the most rare and pure precious metals. Used for jewelry, platinum is usually 90-95% pure. It rarely causes allergic reactions and resists tarnishing. Platinum is considerably denser than gold or silver and is extremely strong and durable.
Point is one-hundredth of a carat. A diamond weighing one-and-half carats weights 150 points.
Polish is one aspect of the external finish of a gemstone. The polish scale ranges from poor to excellent.
|Princess cut |
Princess cut is a square cut, faceted diamond or gemstone. It is a relatively new fancy cut.
|Prong Set |
Prong Set is setting used for diamonds and gemstones whereby a group of claws or prongs hold a gemstone in its mounting.
Quadrillion is a square diamond with 49 brilliant-style facets-21 crown facets, 24 pavilion facets and four girdle facets. It was patented by Ambar Diamonds in 1981.
Radiant is a brilliant-cut square or rectangle with clipped-off corners like the emerald cut. It has 70 facets. The Radiant was first introduced in 1976.
Ratio is 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 aesthetic preferences.
|Round Brilliant Cut |
Round Brilliant Cut gemstones are known to have the most vibrancy and sparkle. With 57 or 58 facets radiating from the center out to the girdle, a brilliant cut maximizes the amount of light that is reflected from the core of the gemstone.
Saturation is the intensity of brightness or dullness of the color. The more color saturated a gemstone is, the more valuable it becomes.
Scintillation is the technical term for sparkle, the tiny flashes of light noticeable in a diamond when the observer moves their head.
|Screw Back |
Screw Back is an ear nut that screws onto a threaded earring post; usually used with diamond stud earrings.
Semi-mount is a setting which is complete except for the main stone, which will be selected separately.
Setting refers to the style in which a gemstone is held by precious metal into a mounting. Common settings include bezel, pave', channel or prong. Setting also refers to the part of jewelry in which one or more stones are set.
Shank is the round body of the ring that encircles the finger, not including the setting.
Shape is the basic outline of the diamond. Round is the most popular and the rest are called fancy shapes. These include marquise, pear, oval, heart, princess, radiant, emerald, trillion and others.
Single-Cut is a diamond with only 16 or 17 facets.
Solitaire is a single stone ring or pendant.
Sparkle is the liveliness of the light reflecting from a diamond; the sum of the brilliance and the fire (dispersion).
|Star Facet |
Star Facet is one of the eight triangular facets found on the upper crown (near the table) of a brilliant-cut diamond.
Symmetry is the description of the uniformity of a gemstone's cut. The scale for symmetry ranges from poor to excellent.
|Synthetic gemstones |
Synthetic gemstones are man made gems, produced in a laboratory, which imitate the characteristics of naturally occurring gems. Often difficult to distinguish from natural gemstones, synthetic gems are typically created with little or no imperfections.
Table is the large, flat, top facet. It has an octagonal shape on a round brilliant diamond.
|Table Percentage |
Table Percentage is the value which represents how the diameter of the table facet compares to the diameter of the entire diamond.
Tone represents how light or dark a stone appears by how much brown, black, gray or white is present.
|Total Depth Percentage |
Total Depth Percentage is the depth of a diamond, from the table to the culet, divided by the average diameter or width of the girdle. The depth of most diamonds is between 53 and 63 percent.
Trillion is the name used as a general term for any brilliant-cut triangle.
|Upper-Girdle Facet |
Upper-Girdle Facet is one of the 15 facets found on the lower crown portion of the diamond (just above the gidle).
Width is the horizontal measurement of an item of jewelry measured across the widest area.