diamond glossary

Listed below, in alphabetic order, are the most widely used terminology regarding diamonds. You may find them helpful when buying a diamond. 

# - A - B - C - D - E - F - G - H - I - J - K - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z

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Abrasion: Tiny nicks along facet junctions producing white fuzzy lines instead of sharp crisp facet edges.

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Baguette: Rectangular Step-cut.

Bezel: A facet on the crown or upper part of the diamond above the girdle.

Blemish: Damage that occurs on the surface of a diamond, which is an imperfection external to the diamond. For example, this would refer to a nick, knot, scratch, abrasion, minor crack or fissure (cavity), or a poor polish.

Bow Tie Effect: An effect caused by a shadowy area visible in some fancy shapes. This is usually due to light leaking out the bottom of the diamond.

Brilliance: Cutting a diamond to the correct proportions increases the reflection of light from the facets and maximizes the brilliance. Brilliance is a combination of luster, light reflection, total reflection, color dispersion and scintillation.

Brilliant Cut: A 57-facet round diamond. This shape and faceting arrangement is designed for maximum brilliance, sparkle and beauty.

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

Burn mark: Surface clouding caused by excessive heat.

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Carat: A unit of weight for a diamond, equivalent to 200 milligrams, or one-fifth of a gram. The word's origin comes from the carob bean, which was used to measure gems in ancient India.

Cavity: A large or deep opening in the diamond

Chip: A tiny piece missing caused by normal wear and tear, or by cutting.

Clarity: Most diamonds, with the exception of internally flawless diamonds, have natural imperfections, commonly referred to as ‘nature's fingerprints'. Inclusions can be white, black, colorless or even red or green. Most inclusions are undetectable by the human eye and can only be seen with 10x magnification. Diamonds are ranked on a scale from flawless (no inclusions visible under 10x magnification) to included (eye visible inclusions). Clarity can also be affected by structure defects or transparency

Clarity Enhanced: A diamond that has been treated to improve its appearance by filling fissures or fractures with a transparent substance. 

Cleavage: The tendency of a crystalline mineral to break in certain definite directions called cleavage planes. The breakage is done by cleaving, a process where a stone is studied so that the plane may be defined and divided with a swift blow.

Clouds: Several extremely tiny inclusions that are too small to be distinguishable from one another. Under a microscope they resemble a milk transparent cloud inside the diamond.

Color: The color of a diamond is ranked on a scale from ‘D' down to ‘Z'. A ‘D' color is the top color grade (colorless) and a  ‘Z' - would mean that stone has a noticeable tint of color, typically yellow. If though, the stone has a greater color saturation than a ‘Z', it is considered a Fancy Colored Diamond and is graded on a separate scale. It is also far more valuable.

Crown: The part of any faceted diamond above the girdle. It consists of a large flat area on top called a table and several facets below it.

Crystal inclusions :  Included minerals in the diamond, which can be colorless, reddish, brownish white, black...

Culet: This is the small facet polished across what would otherwise be the sharp point or tip of the pavilion of a faceted stone, especially a round brilliant cut.

Cut (or Make): This refers to the proportions and finish of a polished diamond. Proportions are the size and angle relationships between the facets and different parts of the diamond. Finish includes polish. Cut affects both the weight yield from rough and the optical efficiency of the polished diamond. A well-cut diamond will internally reflect light from one mirror-like facet to another and disperse and reflect it through the top of the stone. The better cut the stone, the better the sparkle, or 'brilliance'. (See Make).

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Dark Crystal Inclusion: Included crystals that have a dark appearance rather than a transparent or white appearance when viewed under a microscope. They are also known as grain.

Depth: The height of a diamond measured from the culet at the very bottom to the large table facet on the top. The depth is always measured in millimeters.

Depth Percentage (%):  There are two different measurements of a diamond's depth - the actual depth in millimeters and the depth percentage, which expresses how deep the diamond is in comparison to how wide it is. The depth % is critical to creating brilliance and fire in a diamond. A depth % that is too low or too high will cause light to leak out of the stone, causing the diamond to lose sparkle.

Dispersion: When light enters a diamond it reflects off the facets and the angles cut into the stone. This distribution of light is known as dispersion, or the display of the spectral colors.

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Emerald Cut: A style of cutting a diamond in which the outline is a rectangular shape with cut corners and the shape of the facets are rectangular and trapezoid. An emerald is a step-cut

Eye-clean: A diamond that has no inclusions visible to the naked eye - flawless to the naked eye. This is normally true of all diamonds with a grade of about SI-1 or higher on the clarity scale.

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Facets: These are the tiny surfaces polished onto a rough diamond that gives a finished diamond its shape. The way light interacts with these facets affects a diamond's brilliance and sparkle. A round brilliant cut gemstone has a total of 57 or 58 facets.

Faceted Girdle: Sometimes cutters polish the girdle into small facets.

Fancy Shapes: Any diamond other than brilliant round e.g. Marquise, Princess, Heart, Oval, Pear etc.

Fancy Color Diamond: A diamond with an attractive natural color other than light yellow.

Feather: - A feather is a type of inclusion or break in the diamond. It is often white and feathery in appearance and is noted in the stone's clarity grading.

Finish: - Finish describes the exterior of a diamond. The finish is also referred to as the polish and the symmetry of the diamond.

Fire: Often a term used instead of 'brilliance' or 'dispersion'. It is the variety and intensity of colors seen when light is reflected from within the diamond. Good fire can only be achieved with very good to excellent proportions. Also called "refraction" or most often "dispersion" in the trade.

Flaw: An imperfection of a diamond.

Fluorescence: The mostly bluish glow of a diamond in high ultraviolet lighting conditions. Ratings: none, faint, medium, strong. Strong blue fluorescence may cause the diamond to appear oily in daylight. 

Fracture: A crack in the stone.

Full Cut Diamond: A description of a brilliant cut, round stone with 57-58 facets.

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Girdle: The narrow band around the widest part of a diamond.  It divides the crown and pavilion facets. The girdle itself is described by its appearance. The descriptions of girdle thickness range as follows: extremely thin; thin; medium; slightly thick; thick; extremely thick. Whilst it is less desirable for a round diamond to display an extremely thin or extremely thick girdle, such girdle widths are more common and acceptable in fancy shapes.

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Hearts and Arrows: A general term when referring to diamonds with a precise and complete pattern of hearts and arrows achieved by perfect cutting proportions. From the top, a diamond shows an arrows pattern, turn the stone over, and look down on the pavilion and you should see 8 hearts with small 'V' shapes. A true Hearts and Arrows diamond must have all patterns visible at a single glance; this indicates the diamond has optically perfect symmetrical.

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Included Crystal: A mineral crystal contained in a diamond.

Inclusion: A clarity characteristic found within a diamond, also known as 'nature's fingerprints'. These can include a cloud, a fracture, cavities, graining etc. Inclusions can either be visible with the naked eye (usually SI-3 clarity and below) or visible only under magnification. Fewer inclusions mean a finer clarity grade, increased rarity, and increased value.

Internal Graining: Internal indications of irregular crystal growth. May appear milky, like faint lines or streaks, or may be colored or reflective.

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Loupe: A magnifying glass usually of 10X used to examine diamonds.

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Make: See ‘Cut'

Marquise Cut: 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.

Mounting: The portion of a piece of jewelry in which a diamond or other object is set.

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Natural: Small parts of the original surface of a rough diamond left by the cutter when polishing and faceting a diamond. They are usually found on or near the girdle. naked eye.

Needle: A long, thin included crystal that looks like a tiny rod.

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

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

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Pave: Pronounced 'par-vay', is when numerous small diamonds are mounted as close together as possible to create a diamond overlay that covers the metal on which it's set.

Pavilion: This is the bottom portion of the diamond, under the girdle, measuring to the culet.

Pear Cut: A type of fancy shape diamond that resembles a teardrop.

Pinpoints: Miniscule spots internal to a diamond. A cluster of pinpoints can form a cloud.

Pit: A tiny opening, often looking like a white dot.

Point:  A measurement in the weight of a diamond equal to 1/100 of a carat (e.g. 0.25 carats is equal to 25 points).

Polish Mark: Surface clouding caused by excessive heat (also called burn mark, or burned facet), or uneven polished surface resulting from structural irregularities.

Polished Girdle: A girdle that has been lapped or polished to yield a uniform, highly reflective surface.

Princess Cut: A type of brilliant cut fancy shape that can be either square or rectangular.

Proportion: The proportions of a diamond are very important so that the maximum amount of light can be reflected off and out of a stone. The term 'proportion' refers to the relationship between the angles of the facets of the crown and pavilion.

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

Refraction: The change in direction of a ray of light as it enters the diamond.

Rough: The diamond as it comes out of ground before it is cut and polished.

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Scintillation (or Sparkle): The combination of fire (dispersion) and brilliance. It is the amount of light that reflects out of a diamond as it moves. It is also called ‘sparkle'.

Single Cut: A brilliant cut (round) with 17 or 18 facets: 8 bezel, 8 pavilions, a table and a culet facet.

Sparkle: (See Scintillation)

Symmetry: A grade given to the arrangement of the facets and finished angles, created by the diamond cutter when cutting the diamond from its rough to polished form. Grades range from poor to excellent. Poor symmetry will hurt a diamond's sparkle and fire, due to loss of light as it flows through the diamond. Excellent symmetry of a well cut and well proportioned diamond can have a great effect on the diamond's sparkle, or 'brilliance'. 

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Table: The horizontal, top flat facet on the top of a diamond. It is the largest facet on a cut diamond. If the table facet is too large or too small, it will often indicate poor proportions overall.

Table Percentage (%): The width of the table divided by the total diameter of the diamond.

Treated: Diamonds that have been artificially modified to improve their color or clarity. Techniques include laser drilling, fracture filling (clarity enhancement), high pressure high temperature (HPHT) annealing, irradiation, and surface coloration.  

Trilliant Cut: A type of brilliant fancy shape that is triangular.

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