Glossary of Terms


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Abrasion Blemish, such as small nicks along the facet edges, caused by impact damage, polishing or grinding, usually during the cutting or polishing process.

AGS - American Gem Society Established in 1934 by independent jewelers, the institution is dedicated to setting and maintaining standards of ethics and professionalism in the jewelry industry. Since 1996, AGS has operated its diamond grading service through the AGS Laboratories.

AGS Cut Grading Scale 0 - Ideal
1 - Excellent
2 - Very Good
3 - Good
4 - Fair
5 - Poor

Appraisal An estimation of value. For diamonds, this is typically done for sale, insurance assessment or taxation purposes by a professional jeweler skilled in the art of determining value. 

Arrows See Hearts and Arrows.

Artificially Irradiated See Irradiated Diamond.

Asscher Cut See Shape.

Baguette See Shape.

Bearded Girdle Sometimes called bearding, the occurrence ofmany small hairline fractures running from the Girdle into the gemstone.

Bezel The large Facets of the Crown located above the Girdle and below the Table of a gemstone.

Blemish An imperfection on the surface of the gemstone, including scratches, nicks, abrasions, and cracks. Blemishes in diamonds may be natural or caused by external factors, such as poor handling during cutting and polishing or contact with other diamonds during transport. Blemishes diminish a diamond's value.

Bort Low quality diamonds used in industrial applications. See Industrial diamonds.

Bow Tie Effect The appearance of a dark shadow in some Fancy shapes. The cause is said to be a result of light not properly reflecting out of the top of the gemstone. This is sometimes also called a Butterfly Effect.

Brilliance The description of the reflections of light shining from the diamond. Characteristic of a beautiful diamond, brilliance is composed of brightness and contrast. Brilliance is created primarily when light enters through the Table, reaches the Pavilion Facets, and is then reflected back out through the Table, where the light is most visible to your eye. The quality of a diamond's Cut, Clarity, Polish, and Symmetry all play a role in its Brilliance.

Brilliant Cut A preferredCut of diamond where Facets are situated so as to maximize the gemstone's brilliance. A Round diamond with a Brilliant Cut will have 57 Facets, or 58 if there is a Culet. Other popular styles of Brilliant Cut include the heart, marquise, oval, pear, princess (square), and radiant shapes.

Bruise An inclusion or imperfectionat or near the surface typically marked by the presence of associated tiny hairline cracks or feathers

Burned Facet A damaged Facet which appears ash white, as if burnt, usually caused during polishing.

Butterfly Effect See Bow Tie Effect.

Canary A diamond may be described as canary, meaning canary yellow, if it is has yellow hue.

Cape Diamond A pejorative term used to describe any diamond within the yellow Color range of M to Z on the Color grading scale.

Carat The standard unit of measurement used for the weight of gemstones. One Carat is equal to 200 milligrams (one-fifth of a gram). The fractions of a Carat may be expressed as points, with one point equal to 1/100 of a Carat. Weight is one of the most substantial factors in the value of a diamond.

Carbon Spots Common term for black or dark inclusions in a diamond.

Cavity An unfilled or hallow space that is an imperfection in a gemstone.

Certificate A written document from a professional grading laboratory that certifies its evaluation of a gemstone, typically including the gemstone's weight, proportions, Color grade, Clarity grade, Cut grade, and other characteristics and qualities of the gemstone.

Chip An exterior imperfection due to small piece of a gemstone having been broken or cut off.

Clarity The degree to which a diamond is clear of internal imperfections called Inclusions and external imperfections called Blemishes. The imperfections may be carbon or other mineral deposits, impurities, or internal cracks or other natural misformations of the diamond molecular structure. When a diamond is free of significant Inclusions and Blemishes, light is able to clearly pass through the gemstone without interference, enhancing its beauty. A diamond must be viewed under a microscope at 10X magnification by a skilled professional jeweler or grading technician to properly assess its Clarity, as many imperfections not visible with the naked eye can affect the desirability of the gemstone. Inclusions that are observable under 10X magnification may affect a diamond's brilliance. The size, number, position, type, and Color of the imperfections will affect the Clarity grade, which is expressed on a scale of FL (flawless), IF (internally flawless), VVS1 and VVS2 (very, very, slightly included), VS1 and VS2 (very slightly included), SI1 and SI2 (slightly included), and I1, I2, I3 (imperfect). Diamonds without imperfections visible at 10X magnification are referred to as flawless, and are very rare. Rarity affects a diamond's value; the more rare a diamond is, the higher will be its value. The rarity of Diamonds with Clarity grades VVSI, VVS2, VS1 and VS2 also make them more valuable. Clarity is one of the four C's, the primary factors in determining the value of a diamond.

Clarity Enhancement or Clarity Enhanced Repairs or treatments made to fill fractures or Laser Drill holes with glass or resin in an effort to improve the Clarity or appearance of a gemstone.

Cleavage The occurrence in (or characteristic of) a diamond of splitting along planes. Such splitting can occur by exertion of a significant outside force, such as a blow with a diamond cutting tool.

Clouds One or more small inclusions appearing as a hazy, white area inside a diamond, typically only observable under magnification. Depending on their number and size, clouds may negatively affect a diamond's Clarity grade.

Color One of the four primary characteristics commonly graded in diamonds, the Color of a white or clear diamond generally ranges from nearly colorless to yellow. The Color of such diamonds is graded by skilled professional jewelers and grading technicians using a grading scale of D through Z, with the letter grade D given to the colorless and the letter grade Z to a diamond of light yellow color that is not a fancy yellow diamond. The diamonds of Colors other than yellow or yellow/brown, such as blue, pink, green and red are very rare, can be quite valuable, and are not graded according to standard color grading or pricing standards. The Color of fancy diamonds is graded according to hue, depth and saturation of color. Color is one of the four C's, the primary factors in determining the value of a diamond. Color scale of the Gemological Institute of America (GIA):
D, E, F = Colorless
G, H, I, J = Near Colorless
K, L, M = Faint Yellow
N, O, P, Q, R = Very Light Yellow
S, T, U, V, W, X, Y, Z = Light Yellow

Color Enhancement Improving a diamond' Color by one of three methods:
1. HPHT Annealed to remove the appearance of color.
2. Irradiation to improve the color of fancy colored diamonds.
3. Application of a coating (usually to the Pavilion) to either whiten a gemstone, or to add color.

Crown The upper portion of a cut gemstone, from above the Girdle to and including the Table.

Crown Angle The acute angle formed by the intersection of the plane of the Girdle and the plane of the Main Facets of the Crown. The ideal Crown angle is generally thought to be about 34.5°. A Crown angle that is too steep or too shallow can negatively affect a diamond's brilliance.

Crown Height Percentage The height of the Crown divided by the diameter of the Girdle.

Crystal Inclusion An imperfection within a gemstone of crystalline form.

Cubic Zirconium (CZ or Cubic Zirconia) Synthetic (man-made, not naturally occurring) gemstone made to simulate a diamond. Cubic Zirconium is made from zirconium dioxide, which at high temperature transforms to a cubic crystalline form. Cubic Zirconium can be distinguished from diamond by testing for thermal conductivity, as diamonds conduct heat at a greater rate than does Cubic Zirconium, and by measurement of weight, as a Cubic Zirconium stimulant of equal size will be approximately 1.65 times the weight of the diamond.

Culet A flat Facet on the bottom of a cut gemstone. In a round brilliant diamond, an octagonal Facet cut parallel to the Table at the tip of the Pavilion. Pronounced either 'kyü-let or 'k?l-let. Not all round diamonds are cut with a Culet. A large culet is oft

Cushion Cut See Shape.

Cut (or Cut Grade) The quality grade of the fashioning of a gemstone. In cut and polished diamonds, the Cut Grade is a measure of the overall performance (including Brilliance, Fire and Scintillation) and the quality of Polish and Symmetry of the diamond. In Round Brilliant diamonds, the primary Cut proportions include the relationships of Girdle diameter and total length, Table diameter and diameter of the Girdle, the angle of the Pavilion and the angle of the Crown, the thickness of the Girdle and the total depth, Crown star Facet length and length of the Crown, the lower half length and the total Depth, and the Shape, size, placement, alignment and symmetry of the Crown and Pavilion Facets, and point or Culet. Cut is one of the four C's, the primary factors in determining the value of a .diamond. The grading of Cut has not yet been standardized in the industry and can vary depending on the methods, standards, and terminology used by the particular grading laboratories; a grade of "Ideal" by one grading laboratory may actually be the equivalent of a grade of "Very Good" by another.

Cut (shape) Refers to the style of Shape of a gemstone (such as a Round Heart, Marquise or Oval), or the style of faceting (such as Brilliant). See Shape.

Dead Stone A gemstone lacking brilliance due to a multitude of inclusions, or a poor cut.

Depth A measurement of the height of gemstone. In a round brilliant diamond, it is the distance from the point of the Pavilion (or from the Culet, if there is one) to the Table, typically measured in millimeters.

Depth Percentage Depth (height) divided by average width or diameter.

Diamond The hardest known mineral, comprised 99.5% of repeating units of 8 covalently bonded carbon atoms arranged in a cubic formation, and 5% of other trace minerals that give a diamond Color.

Diamond Cutting Processing of cleaving, sawing, bruiting, blocking, grinding, Faceting and polishing rough into cut and polished diamonds. ,

Diamond Gauge An instrument that is used to measure a diamond's length, width and depth in 100ths of a millimeters.

Diamond Grading Report See Certificate.

Digging See Painting and Digging.

Dispersion The separation of light either by refraction or diffraction into the spectrum of Colors, such as in a rainbow.

EGL (EGL-USA) European Gemological Laboratory or EGL is an independent, privately owned, for-profit, Gemological institution founded in 1974 focusing on gemstone certification and research with labs in Antwerp, London, Paris, Tel Aviv, Johannesburg, Mumbai, Seoul, and Hong Kong. EGL-USA became independently owned in 1986 and has labs in New York, Los Angeles, Vancouver and Toronto.

Emerald Cut See Shape.

Extra Facet Any Facet in excess of those normally presented for a particular design.

Eye-Clean When a gemstone has no Blemishes or Inclusions visible to the naked eye (thus, unaided by a magnifying glass or microscope), it is sometimes referred to as being "Eye-Clean."

Face-down (Table down) Relative position of a gemstone when viewed with bottom, Culet and Pavilion side facing the viewer.

Facet The plane surfaces of a polished gemstone, typically created by grinding or polishing. Round brilliant diamonds each have 57 (58 if a Culet is present). Light enters through and interacts with the Facets to produce a diamonds Brilliance, Fire and Scintillation. The number, placement and size Facets will differ among Shapes.

Faceted Girdle A Girdle produced with approximately 32 small flat planes.

Faceting The process of producing Facets, typically by grinding or polishing a gemstone.

Face-up (Table-up) Relative position of a gemstone when viewed with the Table facing the viewer.

Fancy Either a gemstone with a Shape other than a Round Brilliant(for example, a Heart, Princess, Marquis, or Oval Shape), or a colored gemstone with a Color - diamond of natural Color other than light yellow.

Fancy Color See Fancy.

Fancy Shape See Fancy.

Feather An internal imperfection that affects a gemstone's Clarity, typically appearing to resemble a tiny white feather when viewed under 10X magnification.

Fire Term commonly used to describe the flashes of Colored light caused by Dispersion in a cut and polished diamond as light is refracted and diffractedf Generally speaking, the more Fire a diamond has, the greater will be its value.

Fisheye The optical effect created when the Pavilion of a diamond lacks depth resulting ina circular reflection of the Girdle through the Table.

Flaw An imperfection, such as a Blemish, Inclusion, Fracture, or Cavity.

Flawless Without imperfection.

Fluorescence The glow which some diamonds exhibit when exposed to ultraviolet light, such as from a black light.Not all diamonds will exhibit fluorescence. Diamonds that have no fluorescence, or at most faint blue fluorescence, are generally preferred unless the blue fluorescence happens to offset yellow Color in a diamond to make it appear more nearly Colorless. Generally speaking, any fluorescence other than blue will negatively affect value, as will strong or very strong blue fluorescence in diamond of Color grade D-H due to a slight haze that may be present under certain lighting circumstances. Fluorescence is typically graded by its presence, color and intensity as: None, Faint, Medium, Strong, or Very Strong.

Four C's Common term for the four primary grading criteria ofCarat, Cut, Color and Clarity.

Four Grainer A one Carat diamond.

Fracture A significant imperfection consisting of a break in the crystalline structure appearing as a crack, chip or cavity not typically along or parallel to a cleavage plane.

Fracture Filled See Clarity Enhancement or Clarity Enhanced.

Gemstone (Gem) A desirable mineral or petrified organic material that can be used in jewelry after being cut and polished, possessingvarying degrees of beauty, rarity and durability.

GIA The Gemological Institute of America, or GIA, is a reputable, non-profit organization focused on Gemological education, research and certification. GIA boasts six laboratories, thirteen schools and four research facilities internationally.

Girdle The narrow area between the Crown and Pavilion on the outside perimeter of a cut and polished gemstone. A part of the design that can negatively affect durability if too thin and desirability if too think or poorly finished. In a round brilliant diamond, the Girdle is often finished either with or without Facets. The Girdle will typically appear wide (areas called "peaks") and narrow (areas called "valleys") at different places in a round brilliant diamond.

Girdle Thickness The average width of the Girdle, typically measured at the narrow areas (called "valleys"), divided by the diameter of the Girdle.

Grain Weight measure equal to one quarter Carat.

Graining Visible crystal structure in a diamond or other gemstone of crystalline structure presenting as faint streaks, lines, or hazy areas internally or externally.

Hardness The measurement of resistance to permanent deformations (such as scratches). On the Mohs hardness scale of mineral materials, the hardness of a diamond is a 10, the hardest rating of all minerals.

Heart Cut See Shape.

Hearts and Arrows The pattern of geometric shapes resembling hearts and arrows observable in Round Brilliant diamonds of high Cut Grade. Viewed Table-up, the pattern of arrows is observable, and viewed Table-down, the pattern of hearts is observable.

HPHT Annealed High Pressure High Temperature (HPHT) color improvement treatment process for diamonds. Like other treatments to alter the natural Color of a diamond, HPHT makes a diamond less valuable than it might appear.Government regulatory agencies, such as the United States Federal Trade Commission, require artificial enhancement of diamonds to be disclosed at sale.

HRD HogeRaadvoorDiamant (HRD) or Diamond High Council is a private foundation established in Antwerp in1973 to provide diamond laboratory certification services, education and research for the Belgian diamond industry.

Hue Gradation or mixture of the basic spectral Colors of red, orange, yellow, green, blue, violet and purple (such as navy, periwinkle, indigo, teal, turquoise, jade, or aquamarine).Sometimes merely a synonym of Color.

IGI International Gemological Institute, established in Antwerp in 1974, is a privately owned Gemological institution focusing on certification and appraisal, with offices in Antwerp, Bangkok, Cavalese (Italy), Dubai, Hong Kong, Los Angeles, Mumbai, New York, Tel Aviv, Tokyo, and Toronto.

Inclusion An internal, imperfection in a gemstone. Common types of inclusions are: Cavities, Clouds, Crystals, Feathers, Fractures, Graining, Needles, and Pinpoints.
The presence of Inclusions negatively affects value. The fewer Inclusions found in a gemstone, the better will be its Clarity grade. An internally Flawless diamond has no Inclusions observable under 10X magnification.

Industrial Diamonds Diamonds of a quality typically used in industrial tools for cutting or drilling, or other industrial applications. Also known as Bort.

Internal Graining See Graining.

Irradiated Diamond A diamond which has been exposed to radiation for the purpose of altering its Color to a Fancy Color, usually using neutron or electron bombardment. Irradiation makes a diamond less desirable and negatively affects value.Government regulatory agencies, such as the United States Federal Trade Commission, require artificial enhancement of diamonds to be disclosed at sale.

Knot A Crystal Inclusion that extends to the surface of a cut and polished diamond.

Laser Drill Hole Hole created by laser drilling to remove a dark Inclusion to improve Clarity.

Laser Drilling Procedure to remove a dark Inclusion from a diamond for the purpose of enhancing Clarity. Using a high power laser, a tiny hole is drilled and an acid solution is inserted to remove the Inclusion.

Laser Inscription Identification marks engraved by a laser, typically made on the Girdle.

Loupe Small, handheld magnifying glass. A 10X Loupe is the standard instrument used in the Gemological industry.

Loupe Clean A gemstone in which no imperfections are observable under 10X magnification.

Lower Girdle Facet On a round brilliant diamond, a triangular Facet with its short side just below the Girdle on the Pavilion.

Lower Girdle Facet Percentage The average length of the lower Girdle Facets divided by the length of the Pavilion measured from the Girdle (or a plane parallel to the Girdle) to the point or Culet.

Lower Main Facet See Pavilion Facet.

Luster Quality of light reflecting and refracting from the surface of a gemstone.

Make See Cut (or Cut Grade).

Marquise Cut See Shape.

Master Stones (Master Set) Collection of diamonds of Color grades D to Z against which to compare for Color grading purposes.

Melee Small Diamonds, typically less than .20 Carat.

Naturals In a cut and polished gemstone, a Blemish caused by leaving a part of the surface in its rough, unpolished state. This may be done to ensure the gemstone meets a particular weight threshold or because removing the Blemish would cause an inferior Cut. These Blemishes are often found at or near the Girdle.

Needle A thin, straight crystal Inclusion.

Nick A surface imperfection, or damage, where a very small piece of the gemstone has been chipped off.

Open Culet See Culet.

Oval Cut See Shape.

P.C. (or P/C). Per Carat.

Painting and Digging Polishingtechniques used to maximize weight in a cut and polished Brilliant diamond. Painting is done by moving the upper-half or lower-half Facets to positions relative to the Bezels or Pavilion Main Facets such that there is less than optimal definition between them, allowing for the half Facets to be polished very lightly, which is sometimes referred to as "painting on" the Facets. Digging is done byangling the half Facets away from the Bezel or Pavilion Main Facets, which is a technique also employed to "dig out" or remove Naturals near the Girdle. Painting and Digging are usually regarded as signs of inferior workmanship and can negatively affect value.

Pavilion The portion of a gemstone between the Girdle and the Point or Culet.

Pavilion Angle The acute angle formed by the plane of the Pavilionfacet and the plane of the Girdle.

Pavilion Facet One of the four-sided Facets on the Pavilion that meet at the Point or intersect the Culet.

Pavilion Main Facet See Pavilion Facet.

Pear Cut See Shape.

Pillow Cut See Shape.

Pinpoints Inclusions appearing as very tiny white or black dots when viewed under 10X magnification, which when clustered can form a Cloud.

Pit A surface Blemish appearing as a very small hallow, indentation or CAVITY.

Point The tip of a brilliant round diamond at the bottom of the Pavilion if there is no Culet.Also, a common expression of one hundredth (1/100) of a Carat. Other fractional weights of a Carat are also often expressed in Points, such as a one-quarter Carat diamond being 25 points.

Polish The process of finishing a cut and polished gemstone, including grinding to create Facets. Also, the quality of the result of the polishing process, typically graded as: Excellent, Very Good, Good, Fair, or Poor. The Cut grade generally includes the evaluation of Polish.

Polish Lines Surface marks caused by the finishing process if poorly finished or due to an irregular crystalline structure.

Polish Mark See Burned Facet.

Princess Cut See Shape.

Radiant Cut See Shape.

Refraction The deflection of light as it goes from one medium (air) to another (a gemstone), and vice versa.

Rough Diamond A diamond that is not yet cut and polished.

Round Brilliant Cut See Shape.

Scintillation The emission of tiny, brilliant flashes of light. In a cut and polished diamond, Scintillation, sometimes called sparkle, is seen when the observer is in a relatively static position and the diamond is moving, or vice versa.

Shape Theform of a cut and polished gemstone. A gemstone is cut in order to establish its Shape, and therefore the various shapes are typically also referred as a "type of cut," however the Shape of a gemstone should not be confused with its CUT. For cut and po

SI Abbreviation forSlightly Included or Slightly Imperfect, as in the Clarity Grades SI1 and SI2.

Spread Stone A diamond cut in a less desirable fashion, having both a large Table and a short Crown. A diamond with alarger diameter than the weight would suggest.

Star Facet Triangular shaped Facet on the upper part of the Crown adjacent to the Table of a Brilliant Cut diamond.

Step Cut Design or style of faceting arrangement with wide Facets like stair steps in concentric rows parallel to the Girdle. The faceting arrangement of the Emerald and Asscher Shapes are examples.

Surface Graining Blemish appearing as tiny grooves or Facet junction lines. Typically caused by imperfections in molecular structure.

Symmetry The balance of proportions and relative positions of the parts of a gemstone.Also, the symmetrical alignment of Facets in a cut and polished gemstone.A component of Cut. Typically graded as Excellent, Very Good, Good, Fair or Poor.

Synthetic Diamond A man-made gemstone created to simulate a diamond using high pressure high temperature (HPHT) or by chemical vapor deposition (CVD) process. Material properties differ from a Cubic Zirconium. These man-made diamonds can be identified and distinguished from natural diamonds, and trade at substantial discounts.

Table The large top Facet in the center of the Crown of a cut and polished gemstone.

Table Percentage For a round brilliant cut, the average width of the Table (at its eight corners) expressed as a percentage of the average diameter of the gemstone. For Fancy shapes, it is the width of the Table (across the widest part of Table) expressed as a percentage of the width of the gemstone.

Table-up See Face-up.

Treated Diamond/Gemstone A diamond or gemstone which has had its Color or Clarity artificially altered by irradiation, coating or annealing. See Irradiated Diamond.

Trillion Cut See Shape.

Twinning Wisp (Twin Crystals) An Inclusion caused by the irregular structure of two joined crystals, typically appearing as a Cloud.

Upper Girdle Facet On a round brilliant diamond, a triangular Facet just above the Girdle on the crown.

VS Abbreviation forVery Slightly Included or Very Slightly Imperfect, as in the VS1 and VS2 Clarity grades.

VVS Abbreviation forVery, Very Slightly Included or Very, Very Slightly Imperfect, as in the VVS1 and VVS2 Clarity grades.

Zirconia See Cubic Zirconium.

Zirconium See Cubic Zirconium.