Diamond Guide – Diamond Glossary

As you explore this diamond education section, you may have further questions and be inquisitive about the various terminologies associated with diamonds and diamond jewelry. The Diamond Glossary below will give you helpful definitions and terminology.
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Term

Description

Abrasion

Very small and tiny scratches on facet joints which show as 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.

Adamas

The word diamond comes from this ancient Greek word ‘Adamas’, which means unconquerable.

Alluvial

Stones that have been sourced from alluvial deposits in river beds or transported by water and deposited in seas and lake sare alluvial stones. Many gems, including diamonds, are found in alluvial deposits and alluvial diamonds are usually of gem quality.

American Cut

Marcel Tolkowsky’s mathematically calculated ideal proportions and facet angles, to produce maximum brilliancy consistent with a high degree of fire in a round diamond brilliant, are known as American Cut or Ideal Cut.

Appraisal

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

Artificial Diamond

Artificial diamonds are produced by man in a laboratory and mainly used in making artificial jewelry.

Baguette

Baguette is a French word meaning ‘Rod’. It is a step cut for small rectangular shaped diamonds and other gemstones.

Baroque

Diamonds and other gemstones which are irregular in shape or available in freeform.

Bearded girdle

Small or tiny, numerous hair like fractures / cracks around the girdle extending into the stone.

Bezel

A facet on the Crown, or sloping surface just above the girdle of the diamond.

Bezel Facets

On a round brilliant-cut diamond, these eight large, four-sided facets on the crown where the upper points join the table and the lower points join the girdle.

Black Diamond

A diamond with very dark color like dark gray, very dark green or truly black is referred to in the trade as ‘black diamond’.

Blemish

An external mark or surface imperfection on a diamond. For example, a nick, abrasion, knot, scratch, minor crack or fissure (cavity), or a poor polish. A natural or an extra facet is also considered a blemish.

Blue Diamond

A diamond with blue color is very rare and valuable although a fluorescent diamond that shows a blue color in daylight is comparatively common.

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.

Bort

Industrial grade diamonds generally used as drill points.

Bow Tie Effect

An optical effect due to a shadowy area visible in some fancy shapes, caused by light leaking out from the bottom of the diamond. This effect can be minimized by careful cutting using best the proportions and angles.

Briefjes

A special kind of paper which is used to contain diamonds. This paper has several inner leaves of wrinkled bluish paper, which gives a whiter look to the diamonds.

Brilliance

Brilliance describes the reflections of white light returned to the eye from a diamond. Brilliance is produced primarily when light enters through the table, reaches the pavilion facets, and is then reflected back out through the table. Brilliance is the effect that makes diamonds unique among all other gemstones. Although all other gemstones also display brilliance, none have the power to equal the extent of diamond's light-reflecting power. The major factors that affect the amount of brilliancy in a gem are refractive index, proportions, polish and transparency.

Brilliant Cut

Brilliant Cut is the most common style of diamond cutting, which is also used for almost all other gemstones. It is called a brilliant cut because it is designed to maximize brilliance. The standard round brilliant cut consists of a total of 58 facets which covers 1 table, 8 bezel facets, 8 star facets and 16 upper-girdle facets on the crown; and 8 pavilion facets, 16 lower-girdle facets, and usually a culet on the pavilion, or base. Brilliant cut diamonds normally come in round shape, but there are modified variants in other shapes also. Sometimes the term "Brilliant Cut" is also used as a synonym for "Round Diamond."

Briolette

This term is used for a long teardrop shaped diamond with rose cut facets, which sometimes is drilled to be used as a pendant.

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.

Brown Diamond

A diamond with attractive or vivid brown color is rare and considered a fancy colored stone.

Bruise

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

Bruting

Bruting is 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.

Bubble

Any transparent inclusion which consists of a tiny crystal or a grain of a different mineral.

Burnt

A facet may appear burnt or foggy, as a result of the cutter polishing the facet against the grain, or otherwise allowing the diamond to overheat causing the surface to oxidize.

Cachette

A sealed packet containing diamonds bought in a trade deal, along with agreed upon payment terms. This word comes from French word ‘Cacher’ which means to seal.

Cairo Star

A variation on the modern round brilliant cut with 74 facets.

Canary

A term used for diamonds with an intense yellow hue. The yellow color may appear with a very slight greenish or slight orangey shade. Such diamonds are considered Fancy and also called Fancy Yellow.

Carat

The term Carat is used as a standard unit of measurement of the weight of diamonds and most other gemstones. The word comes from the carob beans which are known for their consistent weight and were used in ancient times to measure diamonds and other gemstones. One carat (ct.) equals 200 milligrams, or 0.2 grams (1/5 of a gram), or 1/142 of an ounce. There are 100 points in a carat. If all other factors are equal, the more a diamond weighs, the more valuable it will be. It is sometimes incorrectly spelled ‘Karat’, but Karat refers to the fineness of pure gold and gold alloys.

Carbon

Diamonds are composed of carbon entirely, or almost entirely.

Carbon Spot

An inclusion or imperfection in a diamond that appears black, which is caused by the addition of small particles of graphite or another mineral. In most cases, these black inclusions are not visible to the naked eye, and do not affect the brilliance of the diamond.

Cavity

A type of inclusion consisting of a large or deep opening in the diamond. It may be either internal or extending to the surface caused by cleavage or by a blow. Internal cavities may naturally contain gas, liquid, solid, a combination of two or three of these.

Centenary

A large and famous diamond, unveiled recently in 1988. It was 599 carats in the rough, and cut to a gem weighing over 273 carats. It is second only to the Cullinan for its combination of size and quality.

Certificate

A statement or document issued and certified by a gemological laboratory which conveys the authenticity of a diamond or other gemstone along with the quality and other characteristics.

Change of Color

Sometimes a diamond changes color or appears to be a different color in different types of light. This is caused by selective absorption and/or transmission of the specific type of light to which the stone is exposed.

Channel Setting

A setting style or method in channel form where no metal is displayed between stones.

Chip

A curved break or absence of a tiny piece of a diamond, caused by normal wear and tear, or by cutting.

Clarity

Clarity is one of the four value factors of a diamond 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 the most valuable.

Clarity Enhancement

A process which is used to improve the apparent clarity of a diamond usually by filling fissures or fractures with a transparent substance like glass. Also known as ‘Fracture Filled’.

Clean

A word used by some jewelers unofficially or informally which means flawless, or at least internally flawless.

Cleaning

The cleaning of a diamond is essential to bring or maintain its shine and brilliance. At the mines, various methods are used to clean rough diamonds like boiling in acid etc. For domestic cleaning of diamonds, warm soapy water works well.

Cleavage

The tendency of crystalline minerals, such as diamond, to break in one or more definite directions, producing a more or less smooth surfaces. A cleavage may be caused by inherent internal strain or by a sharp blow. Cleavage is one of the two methods used by diamond cutters to split rough diamond crystals in preparation for the cutting process. The other method is sawing.

Closed Culet

A culet on a diamond which consists of a point rather than a facet. That point is too small to be seen with the unaided eye and can be seen only under 10X magnification.

Cloud

A group of a number of extremely tiny white inclusions which gives a ‘cloudy’ or ‘milky’ appearance under 10x magnification. These clouds cannot be seen with the naked eye and generally does not significantly impact a diamond's clarity grade.

Cluster

This term is used for a diamond ring or any other jewelry containing a number of diamonds. Cluster is also used for a number of kimberlite pipes occurring in close proximity.

Coated Diamond

A diamond colored by a surface coating which masks the diamond’s true body color. Coating may be used extensively on the entire pavilion or limited to one or two pavilion facets or a spot on the girdle.

Color

Color is one of the four value factors of a diamond. Diamonds are ranked on a color scale from ‘D’ (colorless) to ‘Z’ (noticeable tint of color, typically yellow or brown). Diamonds with saturation greater than ‘Z’ color are considered Fancy Colored Diamonds such as blue, pink, purple, red etc. and are graded on a separate scale.

Color Grading

A system of grading diamond colors based on their colorlessness (for other than fancy diamonds) or their spectral hue, depth of color or purity of color (for fancy color diamonds).

Colorless

Colorless diamonds are white or transparent diamonds and widely considered to be of superior quality and desirability.

Color Enhancement

Color enhancement is the improvement process of a diamond's color mainly by irradiation and HPHT (High Pressure, High Temperature). Sometimes color coating is also used to enhance the diamond’s color but is not considered to be the best enhancement process.

Commercial

This term is used for medium to low quality diamonds and is the opposite of fine gem quality.

Commercial White

Commercial White is a dealers’ term for ‘off-white’ diamonds.

Comparison

Sometimes gem laboratories perform their grading by comparing one stone with another stone of known quality. This comparison is useful to consumers who are not well aware of diamond quality factors.

Created

A description of synthetic diamonds as opposed to natural ones.

Critical Angle

Critical angle is the largest angle measured from the normal angle from which light can escape, in an optically dense substance, and the smallest angle to the normal angle at which light is totally reflected within the dense substance.

Crown

The upper portion of a cut diamond above the girdle which consists of a large flat area on top known as the table, and several facets below it.

Crown Angle

The angle between the girdle and diamond's bezel /concentric facets is known as the crown angle. This gentle slope of the facets that surround the table helps to create the dispersion or fire in a diamond. White light enters from the crown angles and breaks up into spectral hues which ultimately enhance the brilliance of a diamond.

Crown Height

The height or depth of the crown of a diamond, above the girdle.

Crystal

A diamond is a crystal which is formed entirely or almost entirely by carbon. Sometimes a crystal is also considered to be a type of inclusion, which is a mineral deposit trapped inside the diamond.

Cube

A cube is a rough diamond with approximately cubic shape. Gem-quality cube-shaped diamond crystals are very rare in nature and considered collector’s items.

Culet

The smallest facet at the bottom of most round or brilliant cut diamonds is known as the culet. Its purpose is to protect the tip of the pavilion from being chipped or damaged. Most modern shapes have either no culet at all, or a small or very small culet.

Cullinan, Cullinan I, Cullinan II

The Cullinan was the largest Diamond Crystal ever found with weight of 3,106 carats in the rough and was cut into 9 major stones and 96 smaller stones. Out of these 9 major stones, Cullinan I is the largest stone with 530.20 carats and Cullinan II is the second largest stone with 317.40 carats. Both of these stones are now part of the British Crown Jewels.

Cushion

A shape of diamond, which ranges from square to rectangular and it has rounded corners and larger facets to increase its brilliance. Cushion cut diamonds are also known as "pillow cut" diamonds.

Cut

Cut is one of the major value factors of a diamond. The cut, also called make, of a diamond refers to the proportions and finish given to the polished diamond by the diamond cutter. Proportions are the size and angle relationships between the facets and different parts of the diamond. It is the only man-made contribution to a diamond's beauty and value.

Cutter

The person who cuts and polishes rough diamonds and converts them into finished diamonds.

Cutting

The process of cutting, grinding or polishing rough diamonds and converting them into finished diamonds.

CZ

CZ denotes cubic zirconium, a widely used simulant/ imitation for a natural diamond. CZ is easily detectable by its 80% higher weight than a diamond of the same proportions or by thermal conductivity testing.

Deep

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

Depth

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

Depth Percentage

The depth percentage, which expresses how deep the diamond is in comparison to how wide it is. In other words, the depth of the diamond is divided by the average width. This depth percentage of a diamond is important to its brilliance and value. The pavilion should be deep enough to allow light to bounce around inside the diamond and be reflected out to the eye at the proper angle.

Detection

Detection is the ability to identify diamond imitations, synthetics and treatments.

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 "Unconquerable". 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 converts them into finished diamonds.

Diamond Cutting

The process of cutting, grinding or polishing rough diamonds and converting them into finished diamonds.

Diamond Gauge

An instrument that is used to measure a diamond's length, width and depth in millimeters.

Diamond Saw

A saw used for dividing or separating diamonds.

Direction

Hardness is directional in diamonds and it is important for cutting. The optimal direction of cutting and polishing depends on the optical axes of diamonds.

Dispersion

Dispersion is the ability of a diamond or other gemstone, to separate white light into the colors of the spectrum. Diamond has the highest dispersion (.044) of any natural, colorless gem.

Draw, Draw Color

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

Drill Bit

Due to diamond’s hardness, it is often used in high quality or high performance drill bits.

Drill, Drilling

Now laser is used to drill a diamond neatly for removing inclusions as well as drilling could also be done to create a diamond bead.

Durability

Durability describes a diamond’s resistance against scratches and cracks due to wear. The durability of a diamond depends on its hardness, toughness and stability.

Dust

Very tiny rough diamonds that are generally used as abrasives. It is also known as diamond powder.

Emerald Cut

An emerald cut diamond is a square or rectangular shaped stone with cut corners. This is also known as Step Cut because it has rows of facets, usually 48 to 50, that resemble a staircase. Due to its larger, more open table, this shape highlights the clarity of a diamond but with fewer facets, this shape has less brilliance than the other shapes.

Enhance, Enhanced, Enhancement

Enhance or enhancement is the process of improving a diamond's color or clarity by using various methods.

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, a diamond‘s proportions were worked out mathematically to enable light to fall 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 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.

Face

A term used for a flat or plane surface, particularly in a rough diamond crystal.

Facet

A plane, polished surface on a diamond which allows light to enter into a diamond and reflect off through different angles.

Faceted Girdle

A girdle of a diamond that is lapped and polished for maximum surface reflection and has many flat planes around the circumference of the diamond.

Faceting

Faceting is the process of placing facets on a diamond.

Fancy Cut, Fancy Shape

Any shape of diamond other than the round brilliant shape is known as fancy cut or fancy shape. It includes marquise, emerald cut, heart shape, pear shape, etc.

Fancy Diamond

A fancy diamond is a Diamond with strong natural body color other than light yellow or light brown. Colored or fancy diamonds are very rare and valuable and available in various colors like blue, pink, purple, red etc.

Feather

Feathers are small fractures in a diamond caused by the tremendous stress that the diamond suffered while it was growing underground. Under magnification, these small fractures appear very much like a feather.

Fill, Filled, Filling

This refers to the practice of filling open fissures in diamonds, usually with glass.

Finish

The term refers to the quality of polish and symmetry on a diamond.

Fire

Fire refers to flashes of spectrum colors seen in a diamond as the result of dispersion.

Fisheye

A diamond with an exceedingly shallow pavilion, which produces a glassy appearance and a noticeable dearth of brilliancy.

Fissure

A crack or fracture or feather, which possibly reaches to the surface of a diamond.

Flat

A diamond with a very thin crown and pavilion which gives a flat effect.

Flaw

A flaw refers to any internal or external imperfection on a diamond and usually includes feather, fissure, carbon spot, knot, etc.

Flawless

Flawless is a term used for a diamond that is without any internal or external flaws when viewed by a trained eye under 10X magnification.

Fluorescence

An effect in many diamonds that makes them glow in ultraviolet rays or light. Diamonds can fluoresce in a number of colors, mainly in blue. Fluorescence ratings include none, faint, slight, medium, strong and very strong. Faint to medium fluorescence is rarely detected under most lighting conditions which include sunlight, whereas strong or very strong fluorescence may make a diamond appear ‘milky’ or ‘oily’ in such lighting conditions. Fluorescence is not dangerous to the diamond or to its wearer. It is a unique and fascinating quality that occurs naturally in a number of gems and minerals.    

Four Cs

A phrase used to describe a diamond's value characteristics which cover the four well-known factors affecting the price of a diamond. All these factors start with the letter ‘C’: cut, color, clarity, and carat weight.

Fracture

A break or chip in a diamond, which usually reaches to the surface of a diamond and that is not in the direction of a cleavage plane.

Fracture Filling

A diamond’s enhancement process in which cavity is filled in a diamond with an artificial substance like glass.

Full Cut Brilliant

A full cut brilliant is a diamond usually with a total of 58 facets, consisting of 32 facets and a table above the girdle and 24 facets and a culet below the girdle.

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)

Gemological Institute of America (GIA) was founded as a 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 standardized the diamond grading system that is used by nearly all other gem labs.

Gemstone

A gemstone is 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

A girdle is the widest part or outer edge of the diamond and the dividing line between the crown and pavilion. The girdle can be rough (matte), faceted, polished or unpolished but a polished or faceted girdle doesn't improve a diamond's grade. Most labs grade a girdle's thickness, not its appearance. The descriptions of girdle thickness range as follows: extremely thin; thin; medium; slightly thick; thick; extremely thick.

Girdle Facet

The 32 triangular facets that are adjacent to the girdle on a brilliant cut or other diamond and split into 16 upper (crown) girdle facets, and 16 lower (pavilion) girdle facets. Sometimes facets are placed directly on the girdle, in which case the diamond is usually said to have a ‘faceted girdle’.

Girdle Thickness

The measurement describing the percentage of the diamond’s average girdle diameter. The girdle thickness ranges as follows: extremely thin; thin; medium; slightly thick; thick; extremely thick. 

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.

Gold

Gold is a yellow precious metal used in most jewelry, usually with various alloys.

Grade

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

Grading

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

Grading Report

A grading report or certificate is a statement, issued by an independent Gemological Laboratory.  At the time of evaluation, the diamond in question has been examined, measured, and scrutinized by experienced diamond graders, using various gemological instruments, and determined to contain the characteristics as stated in the report or certificate. The grading report should accurately describe the proportions, weight, color, clarity, symmetry, polish and possible fluorescence seen in the diamond.

Grain

Diamond crystals have different strength bonds in different directions and these directions are known as grain.

Grain Center

A small area of intense crystal structure distortion which is  usually associated with pinpoints.

Graining

Usually graining refers to internal irregular crystal growth which may appear milky like faint lines or streaks.

Gypsy Setting

The gypsy setting is a recessed setting in which the stone is sunk into the metal and there are often engraved designs around the stone especially in star patterns. The gypsy setting is also known as the ‘star setting’.

Hardest

Diamond is the hardest known naturally occurring substance on Earth.

Hardness

The hardness of a diamond refers to its 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 to the 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 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.

Heat Treatment

Heat treatment is the process in which heat is applied to a gemstone for the purpose of improving its color.

Hope Diamond

The Hope Diamond is the world's largest deep blue diamond. It is famous for its striking color and infamous for its history of bringing bad luck to its owners. This attractive stone also has a history of being stolen and recovered, sold and resold, cut and recut. It is now on display at the Smithsonian Institute in Washington.

Hue

The attribute of a color by virtue of which it is discernible as red, green, etc., and which is dependent on its dominant wavelength, and independent of intensity or lightness. It is a primary factor in viewing and grading fancy colored diamonds.

Ideal Cut

Theoretically perfect cutting proportions and facet angles calculated mathematically to produce maximum brilliancy consistent with a high degree of fire in a round brilliant cut diamond. Ideal cut is also known as American Cut.

IGI
(International Gemological
Institute)

IGI (International Gemological Institute) is an organization which offers a grading report for diamonds and other gemstones. IGI has laboratories located throughout the world, including New York, Antwerp, Mumbai, Bangkok and Tokyo.

Imitation

Imitation is any diamond-like material, either natural or artificial, which imitates a diamond. It is also known as a simulant.

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 is visible to the unaided eye or that has a serious effect on the stone’s durability.

Included Crystal

A mineral crystal is that is embedded in a diamond is known as included crystal. 

Inclusion

An internal imperfection or characteristic which reduces the clarity or brilliance of a diamond. Common diamond inclusions are feathers, crystals, fractures, needles, graining, pinpoints and cavities.

Industrial Diamonds

Low grade or very small diamonds which are not perfect for jewelry use and are generally used in various industrial applications.

Internal Graining

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

Internally Flawless (IF)

A clarity grade which refers to no inclusions and only insignificant surface blemishes.

Irradiated diamond

A diamond which has been exposed to radiation usually to improve its color.

Karat, Karat
Weight

Karat is the American spelling of carat which is now used solely to measure the fineness or purity of gold or gold alloys, whereas the word carat is used with respect to the weight of diamonds or other gemstones. Karat is always based on pure 24 karat gold. For example, if a jewelry item is made of 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. Most diamonds are found in these pipes.

Knot

An included diamond crystal which reaches to the surface of a polished diamond. This knot is difficult to cut or polish because of twinning, negative crystal growth, or similar features.

Kohinoor, Koh-i-noor

The name of Koh-i-noor means "Mountain of Light". It is an Oval Shaped Brilliant cut diamond with a 108.93 carat weight. This diamond was presented to Queen Victoria in 1850 to mark the 250th anniversary of the founding of the East India Company. It is now on display with the British Crown Jewels in the Tower of London.

Laser Drill Hole

A tiny tube which is created in a diamond by laser drilling to treat a diamond. It is one of the few man-made inclusions that can occur inside a diamond. The surface opening may resemble a pit, while the tube usually looks needle like.

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, the 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.

Light Brown

A diamond which is not intense enough to be considered fancy brown and often appears quite white.

Light Yellow

A diamond with a light yellow tint is considered a fancy yellow.

Loupe

Loupe is a French word for a magnifying glass. It is a small magnifying lens used to examine diamonds. 10X magnification is the standard.

Lower Girdle Facet

A diamond facet on the pavilion of a round brilliant cut just below the girdle.

Luster

The quality of reflected and refracted light from the surface of a diamond or gemstone or pearl. Luster is mainly dependent on a 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, and on a step-cut stone, the center row of facets on the pavilion.

Make

Make is a trade term that refers to the proportions, symmetry and polish of a diamond or a gemstone.

Marquise Cut

The Marquise Cut is a traditional shape having elongated ends at both edges. The pointed ends make this shape the most fragile and the most expensive of brilliant style cuts. It has a total of 56 facets and construction of the facets requires a lot of experience. The delicacy of the sharp points demands the utmost precaution. This shape is very popular for engagement rings.

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, settings or larger stones.

Mine

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

Mineral

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

Modern Brilliant
Cut

A round brilliant cut unless otherwise stated, normally with 58 facets including the culet and polished using relatively modern theory. This shape is considered to be ideal for a diamond because it maximizes a stone's sparkle and brilliance.

Modified Brilliant
Cut

A diamond cut in a shape or style other than round brilliant cut, such as oval, pear, marquise, heart, princess, radiant, or baguette.

Mohs scale

A ten-point scale used to measure mineral hardness which was devised by Friedrich Mohs, a German mineralogist, in the 19th century. The diamond is the hardest of all known natural substances and it scores 10 on Mohs Scale.

Moissanite

Transparent silicon carbide, which is a rare crystal in nature, marketed as a diamond simulant. It is named after Henri Moissan, a famous French scientist. It's double refraction is one of the few differences from a diamond, whereas the thermal conductivity is almost equal.

Molecule

Diamonds are composed of large molecules or particles of carbon atoms with strong bonds in all planes.

Mounting

The process of making a ring or other piece of jewelry into which gemstones will be set.

Natural

A small portion of the original surface of a rough diamond left by the cutter when polishing and faceting a diamond which is frequently on or near the girdle. This is generally the sign of a cutter attempting to maximize the weight retention from the rough diamond. Usually naturals do not affect the clarity grade and in most cases, they are undetectable to the naked eye.

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.

Off Make

A poorly proportioned diamond, particularly with poor symmetry.

Old European Cut

The earliest known form of brilliant cut diamond with a very small table, a heavy crown, and usually great overall depth. This is also known as' old mine cut'.

Opaque

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

Orange

A very rare and attractive fancy color of diamond.

Orloff

The Orloff is a Mogul-Cut Rose diamond with a 189.62 carat weight. It has exceptionally pure clarity and slightly bluish green color. According to a tale, the Orloff was set as the eye of Vishnu's idol (one of the Hindu Gods) in the innermost sanctuary temple in Sriangam and was stolen in the year 1700 by a French deserter disguised as a Hindu.

Oval Cut

The Oval Cut is a beautiful Fancy shape which offers great brilliance and fire through its 56 facets. This is an elongated version of a  round cut, and has the same brightness as a round brilliant shaped diamond.

Parcel

A parcel is a paper envelope packed with diamonds which is purchased by a buyer without his selection of the diamonds, although sometimes the buyer is permitted to reject a small number of the diamonds.

Paste

A powder of very small diamonds in paste form, which is made with oil or any other binder and used as an abrasive for cutting and polishing any material including other diamonds.

Pave

An attractive style of jewelry setting in which numerous small diamonds are mounted as closely together as possible to create a sparkly diamond shell. This setting style covers the whole piece of jewelry with a diamond crust and conceals the metal under it.

Pavilion

The pavilion is the lower part of a diamond, below the girdle.

Pavilion Angle

This is the angle between the main pavilion facets and the girdle. In a diamond, this is the most important dimension and an ideal pavilion angle should be around 40.75° to 41°.

Pavilion
Main Facet

The eight facets found on the pavilion of a round brilliant diamond.

Pear Cut

The Pear Cut is a fancy shaped diamond that looks like a teardrop due to its single point and rounded end with 56 to 58 facets. This shape is popular for its uniqueness and brilliance.

Phosphorescence

When a diamond is exposed to daylight, ultra-violet or other light, and continues to glow after the light source has been removed, this is called phosphorescence.

Pick

The term pick is used when a seller permits a buyer to select one or more diamonds from a parcel.

Pink Diamond

Pink is one of the rarest and desirable fancy colors for a diamond. Any diamond with pale reddish, purplish-red and purplish hue is known as pink diamond.

Pinpoint

Tiny or very small inclusions, of pinpoint size, internal to a diamond. A cluster of pinpoints can form a cloud. 

Pipe

This term is used for vertical, columnar rocks that are originated due to lava flow after it has 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.

Platinum

Platinum is a silvery gray precious metal often used for setting or mounting high quality diamonds.

Plotting Diagram

A graphical representation or a diagram in a diamond certificate that illustrates the facets of a diamond as well as the approximate locations and types of internal and external characteristics. These characteristics are internal and external and generally differentiated colors by the colors red and green.

Point

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

Polish

Polish refers to the smoothness of the surface of a fashioned diamond in which optical reflection is maximized. Generally, a polished diamond does not show visible wheel marks or burn marks under 10X magnification. Polish is an indicator of the quality of diamond’s cut which is graded as Ideal, Excellent, Very Good, Good, Fair or Poor.

Polishing

The process of polish which converts a diamond’s rough or irregular surface to a smooth surface by using various methods.

Polished Girdle

A girdle that is polished or lapped to yield a lustrous and highly reflective surface.

Polish Lines

Polish lines refer to tiny or faint surface lines which are visible due to imperfect polishing or irregularities in crystal structure.

Polish Mark

A burn mark or surface clouding on a diamond caused by excessive heat while grinding or polishing.

Powder

The term powder refers to very small diamonds used for polishing other diamonds or materials.

Precious, Precious Stone

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

Price

The price of a diamond is extremely variable and based on all of the aspects of quality.

Princess Cut

The princess cut is a fancy shaped diamond which has pointed corners and is square in shape. The ideal princess cut will have a length to width ratio which is as close to 1.00:1.00 as possible. Princess cut diamonds can range from this perfect square to almost rectangular. This cut is the most popular non-round diamond cut.

Prong Setting

Prong setting is the most frequently used method of setting diamonds into jewelry. This setting usually consists of four or six small metal tips or claws to hold the diamond tightly. This setting allows the maximum amount of light to enter into a diamond from all angles and because of this, the stone appears more brilliant and larger than its actual size.

Proportion

The consideration of each part of a diamond in relation to all other parts. Proportion is an important quality element which evaluates the overall shape of a diamond.

Proportion-scope

A piece of equipment or tool for assessing, measuring and demonstrating the proportions of diamonds either individually or in comparison them with ideal.

Purity

Purity is 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.

Purple

An exceptional and attractive fancy diamond color.

Radiant Cut

The Radiant Cut is 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.

Red Diamond

One of the most rare and desirable colors for diamond.

Reflection

The term reflection refers to the important optical effect where light bounces back or returns once it strikes the surface of a diamond.

Refraction

The term refraction refers to the optical effect where light deviates or changes its direction once it enters into a diamond.

Refractive
Index (RI)

When light meets the surface of a polished diamond, some of the light is reflected, whereas most is absorbed. The light in the diamond slows down and is bent from its original path due to the difference in density between air and stone. This process is known as refraction. This refraction varies from gem to gem depending on density and can be measured and used to help identify the gem type. This measurement is known as the refractive index (RI).

Refractometer

A refractometer is a device that is used to measure the refractive index of gemstones, including diamonds.

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 cut

The round brilliant cut diamond is the most traditional and popular of all the diamond shapes. This cut is considered ideal for a diamond because it maximizes a stone's sparkle. It has 58 facets which offer great brilliance and stability. These 58 facets include 1 table, 8 bezel facets, 8 star facets, 16 upper-girdle facets on the crown, 8 pavilion facets, 16 lower-girdle facets, and usually a culet on the pavilion, or at bottom. This shape of diamond is most commonly used in solitaire diamond engagement rings. 

Saturation

A diamond color's position on a neutral to vivid scale.

Scintillation

This term refers to the display of sparkle or reflection from the polished facets of a diamond visible when the observer is in motion.

Scratch

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

Secondary Deposit

Minerals and/or gemstones that have been separated from their original host rock, usually due to effects of weather, and deposited elsewhere. An alluvial deposit is an example of a secondary deposit.

Semi Precious, Semi Precious Stone

Stones that are valued for their beauty and not one of the four ‘Precious Stones’; Diamond, Emerald, Ruby or Sapphire, are known as semi-precious stones. Semi-precious stones are available in all price ranges from low to high. Semi-precious stones are Alexandrite, Amethyst, Aquamarine, Citrine, Garnet, Iolite, Onyx, Opal, Pearl, Peridot, Tanzanite, Topaz, Tourmaline etc.

Semi-mount

A style of jewelry setting that has the side stones already mounted, but has an empty set of prongs which are intended to mount a diamond center stone as per the customer’s choice.

Setter

A setter is the person who puts diamonds or other gems into jewelry mounts.

Setting

Setting is the process of fixing a diamond or other gem into a mount to create a piece of jewelry.

Shape

A diamond cut by shape describes the outline of the stone and pattern of the facet arrangement. Diamonds are available in various shapes like Modern Round Brilliant, Emerald, Princess, Heart, Oval, Pear etc. Round brilliant is the most popular shape for all jewelry items. All other non-round shapes are called fancy shapes.

Sieve

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

Silver

Silver has been known and used for thousands of years and it is considered to be one of the three precious metals along with gold and platinum. Pure silver is a very soft metal with a lustrous white color. Silver was used as jewelry metal well before the development of white gold alloys, and before platinum could be isolated.

Simulant, Simulated
Stones

A simulated stone can be anything that resembles a natural gemstone but does not have the same physical characteristics or chemical composition. These items are also known as imitation stones and are usually much less expensive than the natural forms. Simulated stones are often made of glass or plastic and most can be detected easily by a jeweler.

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,
SI, SI1, SI2

Slightly Included is a clarity grade that refers to 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.

Sort, Sorting

Usually this term is used to classify rough diamonds into groups depending on their size, color, and surrounding material, whereas in the case of polished diamonds it is used to classify into grades depending on size, color, and clarity.

Spread Stone

A diamond which has been cut with a large table and a thin crown, to retain greater weight. In other words, a diamond which is cut too shallow.

Star Facet

The eight triangular facets that surround the table facet of a round, brilliant-cut diamond. They are named star facets because they form an eight pointed star when viewed from above.

Step Cut

A step cut is a style of faceting arrangement which is named because of its broad, flat planes that resemble stair steps. In this style of arrangement, there are three concentric rows of facets arranged around the table and, on the pavilion, there are three concentric rows arranged around the culet.

Stone

A general term for any gemstone including diamond.

Surface Graining

Surface graining is an indication of structural irregularity in a diamond. Usually parallel lines are visible on the surface or facet edges which look similar to grain in wood. These grain lines are a result of imperfect polishing.

Symmetry

Symmetry is an important aspect of the diamond cutting process which refers to the balance of the outline shape and alignment of the facets. It is graded as Ideal, Excellent, Very Good, Good, Fair or Poor.

Synthetic

A synthetic diamond shares a natural stone's physical, chemical and optical qualities, but it is created in a laboratory. Some modern synthetic diamonds look more natural and are more difficult to identify, but an experienced jeweler or gemologist can usually detect them. 

Table

The table is the flat and the largest facet which is on the top of a diamond. Most of the light enters and exits from this part of a diamond.

Table Percentage

The table percentage is a comparison of the diameter of the table facet to the diameter of the entire diamond.

Tension Setting

A method of setting diamonds and other gems using only the springiness of the mount to hold the stone firm. Although it looks quite spectacular,  it can be unsafe and it should be avoided.

Tiffany

The Tiffany, the fabulous yellow diamond, was found in 1878 in the famous Kimberley Mine in South Africa. It weighs 128.51 carats and was cut as a cushion-shaped brilliant with 90 facets.

Tone

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

Transparent, Transparency

Ideally, a diamond should be completely transparent/clear and any opacity is undesirable.

Treated Diamond, Treatment

Treated diamonds are those which have been processed in some way to enhance their color or clarity. A number of treatment techniques are used to improve the color and appearance of natural and synthetic diamonds. Heat treatment is the oldest method but other techniques include bleaching, dying, laser drilling, fracture filling, high pressure high temperature (HPHT), annealing, irradiation, and surface coloration.

Trigon

Trigon refers to very small triangular marks usually on surfaces of rough and polished diamonds, due to twinning and other crystal growth factors.

Trilliant Cut, Trillion Cut

The Trilliant Cut is a triangular fancy shaped diamond which is also known as Trillion Cut. This shape of diamond looks unique and displays a very sharp brilliance or fire. It may either have pointed corners or more rounded corners.

Twinning

Twinning refers to two or more mineral crystals that have grown together in a symmetrical nature and the growth direction of one crystal has changed or a negative crystal growth has taken place. 

Ultrasonic Cleaner

An ultrasonic cleaner is a tool, generally used by jewelers, to clean jewelry effectively. The ultrasonic vibrations help to free most types of dirt, grime, and oils from these jewelry items. Some ultrasonic cleaners come with a heating unit also. 

Ultraviolet light

Ultraviolet light consists 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

An Upper Girdle Facet is 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,
VS, VS1, VS2

A clarity grade that refers to 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,
VVS, VVS1, VVS2

A clarity grade that refers to 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

You’ll often hear the term “white” applied to colorless diamonds that fall within the GIA D-to-Z color scale or chart. But diamonds in the D-to-Z range are not white at all. Their hues can range from colorless (like a drop of pure water) to having tints of light yellow, light brown or gray. The rarity, and therefore the value, of these diamonds is based in part on how closely they approach colorlessness. All things being equal, the more colorless the diamond, the more rare and expensive it is.

Wisp

A wisp refers to a type of inclusion which occurs due to twinning, or in other words it is an irregularity in the crystal growth.

X-Ray, X-Rays

X-rays are used to sort rough diamonds, as most diamonds fluoresce when exposed to these rays.

YAG

YAG stands for Yttrium Aluminum Garnet which is used as a simulant, so an imitation for a natural diamond.

Yellow Diamond

Generally, most diamonds contain nitrogen which gives them a slight yellow tinge. Diamonds with more intense yellow hue are considered fancy colored diamonds which make them rare and valuable.

Zirconium, Zirconia

Zirconium (cubic zirconium) or CZ is a widely used simulant, an imitation for a natural diamond. It is easily detectable by its 80% higher weight than a diamond of the same proportions or by thermal conductivity testing.



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