Diamond Glossary

Before you begin shopping for a diamond, it’s a good idea to know some basic terminology. Our diamond glossary will give you the ability to look up any unfamiliar terms.

Abrasion: Very small and tiny sketches on facet joints which fabricates white hairy lines instead of sharp crisp facet edges. Antique and other old or heavily used diamonds can have abrasions.

Adamantine: This refers to the surface luster and shine of a diamond.

Alluvial: Stones those have been sourced from alluvial deposits in river beds or transported by water and deposited in seas and lakes. Many gems, including diamonds, are found in alluvial deposits and Alluvial diamonds are usually of gem quality.

Appraisal: Appraisal is a written statement based on estimated retail replacement value of the polished diamonds. Appraisal is mainly used for insurance purposes and should be updated after every few years.

Bezel-setting: In this setting, the stone is secured in the mounting by a thin strip of metal surrounding the stone’s perimeter.

Blemish: A term used to describe external characteristics on the surface of a diamond, such as: nicks, scratches, polish marks, abrasions, naturals and extra facets.

Blue White: A term that has been used for near white diamonds with strong blue fluorescence.

Body Color: A diamond’s actual color which can be observed when examined under a diffused light against a hue less background. The diffused light eliminates glaring reflections and dispersion, which would otherwise confuse the color determination.

Brilliance: Intensity of the internal and external reflections of white light returned to the eye through the crown of a diamond. Proportions, polish, symmetry, clarity and overall workmanship all affect a diamond’s brilliance.

Brilliant-cut: A style of cut of a round stone, where triangular and kite-shaped facets emanate from the center of the stone to the girdle edge on both the crown and pavilion.

Broker: A person who is a specialist in introducing diamond buyers and sellers, and earns his commission on the value of deals done between diamond buyers and sellers.

Bruise: An inclusion which consists surface crumbling and normally accompanied by tiny, root like feathers. This inclusion is usually caused by external trauma such as a knock or a blow.

Bruting: The process of rounding a diamond to form its girdle. This is usually done by grinding one diamond against another on a rotating wheel. It is also known as girdling or rounding.

Carat: The standard unit of weight, not size, used for gemstones. One carat is equal to 0.200 grams. Relative sizes of diamonds by carats Carat weight alone does not determine a diamond’s value. Two stones of equal weight can vary widely in price because of quality differences. In fact, a smaller diamond may actually be more beautiful than a larger stone with inferior cut, clarity, color or presence. When considering diamonds of equal quality, the larger stone will have considerably more value. Usually, a two-carat diamond will be more than twice as valuable as a one-carat stone.The word ‘carat’ comes from the carob tree whose seed was used as the standard of weighing precious stones. Less than 5% of all the diamonds made into jewelry are larger than one carat.

Channel-setting: A setting style, where two parallel metal walls are used to hold gemstones in place, with no metal between each stone.

Chip: Shallow break on a diamond that extends from either a girdle edge or a facet junction. A chip is considered an internal clarity characteristic, and can pose a durability concern.

Clarity: A term used to describe the relative absence of inclusions and blemishes in a gemstone. A diamond’s clarity rating has a direct effect on a diamond’s beauty and price. Virtually all diamonds have imperfections called inclusions and blemishes. A stone is said to be “flawless” if, under ten-power magnification, no external imperfections are visible and no internal flaws are visible. A truly flawless diamond is extremely rare and priced accordingly. All gem-grade diamonds can receive a clarity rating based on an industry standard scale: FL (flawless) to I3 (heavily included).

Cloud: A type of inclusion composed of numerous pinpoints. Pervasive clouds can cause a hazy or milky appearance in a diamond.

Color: The basic hue (body color) of a diamond when brilliance and dispersion are ignored. The saturation of color is judged against a predetermined scale. The colored tinting found in most diamonds is caused by minute impurities within the stone. The untrained eye is incapable of making the color evaluations that can affect the value of a stone by thousands of dollars. The color of each diamond is determined by comparing it to authenticated “master diamonds”. Each stone is then color-graded to a precise scale from “D” (colorless) to “Z” (saturated).

Crown: The part of a diamond above the girdle plane.

Culet: Small, octagonal facet on the point of the pavilion on some brilliant-cut diamonds or a rectangular facet on the keel of some step-cut diamonds.

Cushion shape: Term used to describe a diamond with a rectangular or squarish girdle outline, curved sides, rounded corners and brilliant-cut facets. Another name for oval cut.

Cut: Refers to the facet proportions on the surface of a diamond, its polish and symmetry. More than any other factor, the precision of its facets determines the beauty of the stone. There is a tradeoff between quality and size. When a stone is cut to maximize brilliance, dispersion and scintillation, it usually loses size. More of the stone must be cut away. Conversely, when cut for size, the diamond usually loses brilliance, dispersion and scintillation.

Deep: This usually means a diamond which has been cut too deep. This deep cut maximizes weight but sacrifices brilliance.

Depth: The height of a diamond from the table to the culet which is measured in millimeters.

Diameter: The width of the diamond, as measured across the widest part of the girdle.

Diamond: The word “diamond” comes from the Greek word “Adamas”, meaning “Unbreakable”. Diamond is composed of carbon that crystallizes in the “cubic,” or “isometric,” crystal system. It is the hardest known substance in the world (10 on Mohs’ scale). The Diamond is uniquely resistant to damage by heat or scratching, and can be cut or polished only by another diamond. It occurs in colors ranging from colorless to yellow, brown, orange, green, blue, and violet.

Diamond Cutter: The person who cuts and polishes rough diamonds and convert them into finished diamonds.

Diamond Cutting: The process of cutting, grinding or polishing rough diamonds and convert them into finished diamonds.

Diamond Gauge: An instrument that is used to measure a diamond’s length, width and depth in millimeters.

Dispersion: The breakup or separation of white light into spectral colors, each having its own wavelength and frequency. Synonymous with “fire.”

Draw, Draw Color: A diamond which is not pure white (colorless) is often said to draw color.

Emerald-cut: Rectangular or square step-cut stone with diagonally cut corners and two, three or four rows of facets parallel to the girdle on the crown and pavilion.

Enhancement: An unnatural process that alters the appearance, particularly the color or clarity, of a natural diamond or other gemstone. Coating, irradiation, high temperature/high pressure, fracture filling and laser drilling are all examples of enhancement. The only acceptable enhancements are cutting and polishing. Synonymous with “treatment.”

European Cut: A European version of ‘ideal’ cut which was used and preferred in Europe although it was never adopted as a common form of cutting.  In this cut, diamond‘s proportions were worked out mathematically for light falling perpendicularly on the crown.

Extra Facet: An additional facet placed onto a diamond, usually to remove a ‘natural’ or small surface blemish. This extra facet is not required by the cutting style and symmetry.

Eye Clean: A term used in the jewelry industry to describe a diamond with no blemishes or inclusions that are visible to the unaided eye.

Facet: Flat, polished surface on a fashioned gemstone.

Fancy shape: Any shape other than a round-brilliant or single cut. Includes: , pear, marquise, oval and heart shapes.

Feather: Any cleavage or fracture on or below the surface of a gemstone. The appearance is usually white when viewed at a right angle to the break.

Finish: Quality of a diamond’s polish, condition of its girdle, and the precision of the faceting arrangement.

Fire: The breakup or separation of white light into spectral colors, each having its own wavelength and frequency. Synonymous with “dispersion.”

Fisheye: A diamond can be fashioned with a shallow pavilion and large table, to give the impression of a much larger stone. This technique produces a dull stone, and even worse, it creates an ugly “fisheye” effect when viewed through the crown.

Fluorescence: Emission of visible light by a material when it is exposed to certain energy sources, such as radiation or ultraviolet light. Fluorescence only continues as long as the material is exposed to the energy source.

Four C’s: The popular and overly simple four factors — cut, clarity, color and carat weight, which are commonly used to determine the value of a diamond. These factors alone are an insufficient measure of a diamond’s true quality, beauty and value.

Gauge: Any device or instrument which is used to calculate the weight of diamonds, by measuring or estimating physical dimensions like diameter, depth, length.

Gemologist: A person with expertise in gemology is known as gemologist. There are many recognized courses available from various Gemological Institutes which offer study in gem identification, grading and pricing, as well as diamond grading and appraising.

Gemological Institute of America (GIA): Was founded as non-profit organization in 1931 by Roger Shipley. GIA maintains the highest standards for grading diamonds and other precious gems and it has one of the world’s most-respected and well-regarded gemological laboratories. GIA has developed and standardize the diamond grading system that is used by nearly all other gem labs.

Gemstone: A mineral or rock, which can be used in jewelry after cutting or faceting and polishing. Gemstones are diverse in their beauty and many gems are available in a stunning variety of colors. Most gemstones have little beauty in the rough state. They may look like ordinary rocks or pebbles. After a skilled cutting and polishing of a gem, full color and luster can be seen.

Girdle: The narrow band that circumscribes the edge of the plane intersecting the crown and pavilion of a diamond. The girdle may be polished, faceted or bruted (rough surface).

Girdling: Girdling is the process of giving a circular shape to a diamond. In this process, a diamond is held in a lathe, or in a cutting machine, and cut or shaped by another diamond, called a sharp.

Grade: A recognized measure of an aspect of diamond’s quality, mainly clarity and color.

Grading: The process of evaluating a diamond, and allocating grades to it.

Graining: Internal or external lines commonly found on a diamond which show the growth pattern of the crystal structure. Grain lines are often the result of growth inconsistencies and cannot be removed by recutting the diamond. Significant graining can severely affect the beauty of a diamond.

Hardness: The hardness of a diamond refers it’s resistance to scratching on a smooth surface. Diamond is the hardest known substance on Earth and it is graded 10 on Mohs’ scale of hardness. Hardness is directional in most gemstones.

Head: Head refers part of the setting that holds the center stone or solitaire in place.

Heart Cut: The Heart shaped diamond is a fancy cut diamond and essentially a pear-shaped with a cleft at the top and which typically contains 59 facets. Due to the complexity of the shape, skilled cutting is necessary to maintain the diamond’s brilliance. Generally people prefer a heart shape diamond for sentimental purposes. This shape is mostly used in pendants, but also suitable for most jewelry items.

Hue: Hue is an aspect of color such as pink, yellow, blue, green, etc. It is a primary factor in viewing and grading fancy colored diamonds.

Imperfect: The diamond imperfection grade at the low end of the ‘flawless-to-imperfect’ scale. An imperfect diamond contains any external blemish or internal inclusion or flaw that are visible to the unaided eye or that have a serious effect on the stone’s durability.

Inclusion: Any internal clarity characteristic of a diamond. Large or numerous inclusions are considered flaws that seriously diminish the value of a gem. Virtually all diamonds have imperfections called inclusions and blemishes. A stone is said to be “flawless” if, under ten-power magnification, no external imperfections are visible and no internal flaws are visible. A truly flawless diamond is extremely rare and priced accordingly. All gem-grade diamonds can receive a clarity rating based on an industry standard scale: FL (flawless) to I3 (heavily included).

Internal Graining: A diamond which contains internal irregular crystal growth is known as internal graining. It may appear milky like faint lines or streaks.

Internally Flawless (IF): A clarity grade which refers no inclusions and only insignificant surface blemishes.

Karat, Karat Weight: Karat is the American spelling of carat which is now only used for gold or gold alloys weight whereas English spelling carat is used in respect of weight of diamonds or other gemstones. Karat is always based on pure 24 karat gold and if a jewelry item contains 18 karat gold that means it has eighteen parts pure gold and six parts other metal alloys.

Kimberlite Rock: The yellow or blue rock which forms diamond pipes, and in which most diamond is found.

Knot: A diamond crystal within another diamond crystal. Such inclusions are considered flaws and often cause a problem with the overall polish of the diamond and cannot be easily removed.

Laser Drill Hole: The result of an enhancement process used to improve the appearance of a diamond with dark or black inclusions. A laser is used to drill a hole to reach the inclusion surface where it can then be bleached with acid.

Laser Drilling: A diamond enhancement technique by a laser which is used to drill a diamond to remove inclusions. BY using this laser drilling technique, clarity grade of a diamond can be raised.

Length-to-Width Ratio: A comparison of the length and width of the girdle outline on fancy shaped diamonds. It is used to analyze the outline of fancy shapes only and it is never applied to round diamonds. The ratio is found by dividing the length of the diamond by the width where diamond width is always stated as 1. This ratio is simply a matter of personal aesthetic preferences and there is no defined ideal ratio for any of the fancy shaped diamonds.

Luster: The quality of reflected and refracted light from the surface of a diamond or gemstone or pearl. Luster is mainly dependent on stone’s surface (polish) and the reflective index of the mineral. Luster can be described as: adamantine, pearly, greasy, metallic, silky, resinous, vitreous, earthy (also known as dull) and waxy.

Main Facets: The large crown and pavilion facets of a brilliant-cut diamond whereas on step-cut stone, the center row of facets on the pavilion.

Marquise shape: Elongated brilliant-cut with two curved sides and two pointed ends.

Master diamonds: A set of polished diamonds of known body color and saturation to which other diamonds can be compared to assess their color grade.

Melee: This term is used to describe small brilliant-cut diamonds under .20 carat. Generally, these small diamonds or gemstones are used to embellish mountings, setting or larger stones.

Milgrain: A finishing detail on metal work that produces a beaded effect along the edge of the metal.

Mine: A place where diamonds are extracted from the ground, by using various methods of mining like open cast, deep pit etc.

Mineral: A naturally occurring, inorganic element of the Earth with a consistent atomic structure and chemical composition.

Modified brilliant: A type of faceting arrangement which features varying rectangular girdle outlines and cut corners with the number of facets greater or less than the standard 57 or 58 found on a round-brilliant.

Mounting: See setting.

Nailhead: When the pavilion of a diamond is too deep, a darkening “nailhead” effect appears in the middle of the stone.

Natural: A portion of the original surface of the rough diamond which has been left on a polished diamond. This practice maximizes carat weight but may compromise beauty.

Needle: A long, thin and sharp crystal inclusion which looks like a tiny rod.

Nick: A minor chip out of the surface of a diamond, usually found near or on the girdle of the stone

Oval Shape: A brilliant-cut diamond with an elliptically shaped outline having two curved sides and two rounded ends.

Opaque: Refers to the transparency of a diamond. Generally opaque material does not transmit light.

Pavilion: The portion of a diamond below the girdle, including the culet.

Pear shape: A brilliant-cut diamond with a pear-shaped outline having two curved sides, one rounded end and one pointed end.

Polish: The overall condition of a facet’s surface on a fashioned diamond.

Presence: This evaluation includes precision of cut, symmetry and polish. Individually, and as a group, they influence a diamond’s beauty and overall appearance. The shape, size and angle of each individual facet is crucially important. The expert diamond cutter must follow a prescribed geometric plan to produce an “excellent” precision of cut. The quality of a stone’s polish directly influences a diamond’s brilliance, dispersion and scintillation.

Phosphorescence: A diamond, which is exposed to daylight, ultra-violet or other light, continues to glow after the light source has been removed.

Pipe: This term is used for vertical, columnar rocks that are originated due to lava flow and after that cooled and solidified in the neck of a volcano.  When these rock masses consist of kimberlite, they often contain diamonds.

Pit: A tiny opening or surface mark on a diamond which often looks like a white dot.

Point: A unit of measurement which is used to describe the weight of diamonds where one point is equivalent to one-hundredth of a carat. For example, a 1/2 carat diamond weighs 50 points.

Precious: The term precious is used for stones as well as metal. Stones those are highly valuable for their hardness and rarity, are known as precious stones. Precious stones include diamonds, emeralds, rubies, and sapphires.

Prong: Part of the metal setting designed to hold the diamond in place.

Proportion: The relative dimensions and angles of a diamond’s faceting and the relationships that exist between them.

Purity: Also known as clarity which describes the absence or presence of flaws inside or on the surface of a diamond. Diamonds are graded on a scale from Flawless (no inclusions or blemishes visible under 10x magnification) to Included (eye visible inclusions or blemishes). If other factors are equal, flawless stones are most valuable.

Radiant Cut: A fancy shaped rectangular or square diamond with cut corners. This shape comes with 62 to 70 facets and offers the elegance of the emerald shape with the brilliance of the princess shape. Trimmed corners are the signature of this shape, and they help to make the radiant cut a popular and versatile choice for jewelry.

Ratio: The term ratio is also known as length to width ratio which is a comparison of the length and width of the girdle outline on fancy shaped diamonds. It is used to analyze the outline of fancy shapes only and it is never applied to round diamonds. The ratio is found by dividing the length of the diamond by the width where diamond width is always stated as 1. This ratio is simply a matter of personal aesthetic preferences and there is no defined ideal ratio for any of the fancy shaped diamonds.

Reflection: The term reflection is used for important optical effect where light bounces or returns once it strikes the surface of a diamond.

Refraction: The term Refraction is also used for optical effect where light deviates or change its direction once it enters in a diamond.

Rough: The term rough is used for any uncut or unpolished diamond.

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

Round-brilliant: A traditional diamond shape based on the octahedron rough crystal. It has 57 or 58 facets consisting of a crown, girdle and pavilion. The crown has a table, 8 kite-shaped bezel facets, 8 star facets, and 16 triangular upper-girdle facets. The girdle circumscribes the diameter and may be either faceted or bruted. The pavilion contains 8 kite-shaped main facets, and 16 triangular lower-girdle facets. It may or may not have a culet on the pavilion.

Scintillation: The flashes of reflective light emanating from a diamond’s polished facets are observed when either the diamond or light source is moved. Scintillation is often referred to as “sparkle”.

Scratch: A narrow, shallow, elongated nick on the surface of a diamond which usually appears as faint white lines, curved or straight, under magnification.

Setting: The entire metal mounting holding the polished diamond or diamonds. The design and workmanship of the setting is critical to the overall beauty of a diamond ring. Synonymous with “mounting.”

Shape: The face-up girdle outline of a polished diamond or gemstone.

Shared-setting: A setting style in which a pair of centrally positioned prongs holds two stones—one to its right and one to its left.

Sieve: A tool for sorting rough or polished diamonds by size. Diamond sieve sets have interchangeable sieve plates each drilled with different sizes holes.

Single Cut: A very small round diamond with only 17 or 18 facets, instead of the normal 57 or 58 facets of a full cut round brilliant. These facets include 8 bezel, 8 pavilions, a table and sometimes a culet facet.

Slight Inclusions: Slightly Inclusion is clarity grade that refers slight inclusions in a diamond which are easily visible under 10X magnifications. It is graded as SI1 and SI2.

Solitaire: A ring or any other piece of jewelry containing a single diamond or other gem. This style is very popular in rings.

Star Facet: The eight triangular facets that surround the table facet of a round, brilliant-cut diamond. It is named star facets because they from an eight pointed star when viewed from above.

Step-cut: A cutting style in which narrow, rectangular diamond facets are arranged in rows parallel to the girdle on both the crown and pavilion.

Symmetry: A term used to describe the precision and exactness of the facet placement on a polished diamond.

Table: The large facet in the center of the crown of a polished diamond. On a round-brilliant-cut diamond, the table is octagonal in shape.

Tone: An attribute of color which determines its lightness or darkness of shading and important in grading fancy colored diamonds.

Trapeze: Trapezoid shaped cut diamonds, usually placed at the sides of a solitaire, or in ensembles of diamonds on a jewel.

Transparent, Transparency: Ideally, a diamond should be completely transparent and any opacity is undesirable.

Ultraviolet Light: Short wavelengths in comparison of visible light’s wavelengths and due to this it is invisible to naked eye. Ultraviolet light is in between visible light and X-rays.

Upper Girdle Facet: Any of the sixteen facets on the crown, adjoining the girdle of a diamond.

Vivid: The term vivid is used for color grading of fancy colored diamonds to denote the most intensely colored stones.

Very Slight Inclusions: It is a clarity grade that refers minor or slight inclusions in a diamond which are difficult to see under 10X magnifications. It is graded as VS1 and VS2.

Very Very Slight Inclusions: It is a clarity grade that refers tiny or very slight inclusions in a diamond which are extremely difficult to find, even under 10X magnifications. It is graded as VVS1 and VVS2.

White Diamond: White diamonds are transparent or colorless and promoted as the best, but only because other attractive colors are extremely rare.

Wisp: Refers to a type of inclusion which occurs due to twinning or in other words it is an irregularity in the crystal growth.

Yellow Diamond: Generally most diamonds contain nitrogen which gives them a slight yellow tinge. But diamonds with more intense yellow hue are considered as fancy colored diamonds which make them rare and valuable.

4 C’s: All diamonds share certain features that allow us to compare and evaluate them. These features are called the 4Cs: Carat weight, Clarity, Color and Cut.