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Diamond Glossary

Diamond Glossary


Parts of a diamond:



The width of the diamond as measured through the girdle.

Table: The table is the largest facet of a gemstone.

Crown: The crown is the top portion of a diamond that extends from the girdle to the table.

Girdle: The girdle is the narrow band around the widest part of a diamond.

Pavilion: Known as the bottom portion of the diamond, the pavilion extends from the girdle to the culet.

Culet: The culet is the small facet at the tip of the stone. The culet protects the tip of the pavilion from being chipped or damaged. For the preferred cut, the culet is either graded “small” or “none” and is not visible with the unaided eye.

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



American Gem Society (AGS):

The AGS is a highly respected educational institution for gemological studies that was established in 1934. Expert gemologists grade diamond quality and provide grading reports. The AGS has its own grading system for determining the quality of a diamond’s cut. Their ranges are as follows: 0, the most ideal to 10, the most poorly cut.


AGS Cut Grading Scale

2-Very Good
3, 4- Good
5, 6, 7-Fair
8, 9, 10- Poor



Considered as a mixture or solid solution of two or more metals, common alloys include gold under 24kt (a mix of silver, copper and other metals) and sterling silver (silver and copper).



Known as the diamond center of the world. Antwerp is the home of Antwerp Original Diamonds. It is also the second largest port of Europe on the river Scheldt, which is located in Belgium.



An appraisal is a written and unbiased, professional opinion of the diamond’s quality and value. This would include information about the diamond’s cut, color, clarity, carat weight as well as the dimensions and the estimated value of the diamond.


Baguette Shape:

Used for small gems, the baguette shape has a rectangular style to it. The French word meaning “rod”, the baguette shape has rows of step like facets.



Refers to the scratches and other imperfections on the surface of the diamond.                                     



The sparkle in the stone that gives the diamond a glowing effect, caused by its light-reflecting ability. It is created when light enters through the table and is reflected back up to the surface, creating a “shine” that is very visible to the naked eye.


Brilliant Cut:

The brilliant cut is one of the three styles of faceting arrangements.  The brilliant cut is proven to reflect the most light from within the stone. This cut is specifically designed to maximize the brilliance of the diamond. Shapes with a brilliant cut include round diamonds, ovals, radiants, princesses, hearts, marquises, and pears.



A carat is a unit of weight by which diamonds and gemstones are measured. One carat is equivalent to 200 milligrams, or 0.2 grams.




Decimal Equivalent

1/10 ct


.09 - .11

1/8 ct


.12 - .13

1/7 ct


.14 - .15

1/6 ct


.16 - .17

1/5 ct


.18 - .22

1/4 ct


.23 - .28

1/3 ct


.29 - .36

3/8 ct


.37 - .34

1/2 ct


.45 - .58

5/8 ct


.59 - .68

3/4 ct


.69 - .82

7/8 ct


.83 - .94

1.0 ct


.95 - 1.05


Carat Total Weight (

The combined total weight of all the stones in a piece of jewelry is called the carat total weight.


Carbon Spots:

A term used to describe the appearance of certain inclusions and blemishes in a diamond. Carbon spots are dark inclusions found in the diamond. In most cases, carbon spots cannot be detected with the naked eye.



Gemologists provide certificates with diamonds in order to prove its authenticity and value. These certificates are also known as “diamond grading reports”, “diamond dossier” or “diamond quality report”. These gemologists are experts in their field who analyze the diamond’s characteristics, such as color, cut, carat weight, finish, dimensions, as well as other qualities to determine its value. (See grading reports)



The clarity of a diamond refers to the number, position and size of inclusions that are naturally located inside the diamond. To better understand the clarity, the GIA (Gemological Institute of America) grades as follows:

FL- Flawless. No internal or external flaws and blemishes.

IF – Internally Flawless. Free from internal flaws. May contain 
                external blemishes that can be easily removed by polishing.

VVS1, VVS2 – Very, very slightly included. Contains minute inclusions 
                that are very difficult to see under 10 x magnification.

VS1, VS2- Very slightly included. Inclusions include small crystals, 
                feathers and clouds when observed. Difficult to see inclusions under 10 x magnifications.

SI1, SI2 – Slightly included. Easy to detect inclusions under 10 x magnifications. May not    be visible to the naked eye.

I1, I2, I3 – Included. Flaws and blemishes are easily seen. Diminishes 
the brilliance of the diamond.



Cleavage is the area of the diamond where bonds are weak. Diamond cutters usually split gemstones in order to separate rough crystals.



Clouds are small inclusions found within the diamond. They are too small to be detected with a microscope, much less with the unaided eye. This grouping inside the diamond does not usually impact a diamond’s clarity grade.



Diamonds are graded on a scale based on their color. Also one of the four C’s, the color of the diamond plays a huge part in determining the quality of the diamond. The GIA and AGS are widely known for their grading system. It ranges from D (absolutely colorless) to Z (light yellow-brown). The more colorless the diamond, the more valuable and rare it is.



The upper portion or the top of a cut gemstone that is located above the girdle. The crown height is the measure between the girdle to the table when viewed sideways.



The smallest facet located at the bottom of the diamond. The purpose of the culet is to prevent the tip of the pavilion from being damaged, whether by impact or wear. The preferred culet is usually small, or some chose to have no culet at all.


The cut refers to the angles and proportions of a polished diamond. It is one of the four C’s that plays an important part in determining the diamond’s brilliance. There are three types of cuts: Ideal, Shallow and Deep cut.

Ideal Cut- Having an ideal cut diamond reflects the true beauty of the 
diamond. Light is reflected from one facet to another and is reflected 
back to the surface of the diamond. It shines with glamour, sparkles 
with grace, and is cut to perfection.

Shallow Cut- When light travels through a shallow cut diamond, the 
light is cast away through the bottom of the stone, which then lessens 
the allurement of the diamond because of its lack of “sparkle” and zeal.

Deep Cut- Light traveling through a deep cut diamond is lost through 
the sides of the diamond, causing the diamond to appear dark and even 



Refers to the height of a diamond from the culet to the table. The depth is usually measured in millimeters.


Depth Percentage:

The depth percentage compares how deep the diamond is (from the table to the culet) to how wide the dimensions are (from girdle to girdle). Ideally, the depth of the pavilion should be just deep enough to allow light to enter and reflect back at an angle that will catch an observer’s eye.



The diamond is the hardest natural substance known to man. It is a crystallized carbon known for its usefulness in tools and is valued universally as a gem. It rates as a 10 on the Mohs Scale, which is the highest on the scale. The quality of the diamond can be rated using the four C’s (cut, color, clarity and carat weight). It is also the birthstone for the month of April.


Diamond Cutting:

Diamond cutting is a method that is used by diamond cutters to shape a rough, unpolished diamond that has been mined from the depths of the earth into a finished and polished stone.

Diamond cutters usually separate the rough gems into smaller pieces, making them easier to shape. They then grind the edges of the gem and make it outline a shape (a heart, oval or circle shape). The next step would then be to shape the main parts of a diamond (the table, the culet and the pavilion). After it has been analyzed, the gem is then boiled into hydrochloric and sulfuric acids to remove debris and other unwanted elements for a polished and finished look.


Diamond Gauge:

A tool used to measure a diamond's length, width and depth in millimeters.


Emerald Cut:

The emerald cut is a diamond shape that can take form as a rectangle or a square. It is also referred to as a step cut, to resemble steps on a staircase.


Eye Clean:

Eye clean is the term one uses to describe a diamond with no inclusions that can be seen with the naked eye.



The facets are the smooth and polished, tiny flat faces on the surface of the diamond.



The feather is a small inclusion or flaw found within the diamond. It is shaped like a white feather when viewed under a microscope, but will not affect the beauty of the diamond. However, these inclusions on the diamond, based on the depth or location, can make the gem more vulnerable to cracking.



An imperfection or inclusion found on the diamond.



A faint blue tint that might be seen within the diamond under ultraviolet light is the fluorescence of a diamond. Even though it might not be seen under the untrained eye, gems that give out a strong blue color might appear oily when reflected in daylight. Even though it is not considered a grading factor, you can still judge the gems by its ratings:






                                -Strong Blue



A break or inclusion on the surface of the diamond that might appear like a splinter is called a fracture. This can be resolved by “filling” that break with an artificial substance. Filling fractures can only be detected when viewed under a microscope.


GIA (Gemological Institute of America):

The GIA is a highly respected institute dedicated to the knowledge and understanding of diamonds. They had founded the universally recognized 4 C’s (cut, color, clarity and carat weight) and is considered as the  “Harvard of gemology”. Established in 1931, the GIA had earned the respect and trust of jeweler companies and its communities around the world.



The girdle is the narrow band that separates the pavilion and the crown of the diamond. It is also known as the widest or the outermost edge of the diamond.


Grading Report:

The grading report is a certificate that states the diamond’s cut, clarity, color and carat weight. This certificate also includes that dimensions and the proportions of the diamond as well as the imperfections, blemishes and other characteristics that might be significant to the diamond owner. (See certification)



The head is the part of the diamond that secures the center of the stone in a setting.


Heart-Shaped Cut:

The heart-shaped cut is formed like a pear with a cleft at the top and is made to resemble the symbol for Valentine’s Day. This cut is the universal symbol for love and romance.



Also called a simulant, an imitiation diamond is a laboratory made gemstone. Even though it is much more inexpensive than the real thing, imitation diamonds such as cubic zarconia can easily be determined by experts as being faux. However, to the casual observer, they can strongly resemble real diamonds.



An inclusion is a natural characteristic found within the diamond. Types of inclusions include imperfections in the form of feathers, clouds and crystals.


Internal Grading:

Indications found within the diamond that might show signs of abnormal crystal growth. Streaks and lines may appear on the diamond as well as traces of color.


HRD (Hoge Raad voor Diamant):

The HRD is a reliable, European laboratory that grades gems. The HRD is based in Antwerp, Belgium and is designed to evaluate the quality of gems.


Irradiated Diamond:

An irradiated diamond is a diamond that has been treated with a form of radiation. In order to change or improve the color of the diamond, jewelers had decided to submerge the gems in reactor cores and other radioactive elements.



A crystal diamond found within another crystal of the diamond is referred to as a knot. Knots are very difficult to remove and might be considered an imperfection of the diamond.


Laser-Drill Holes:

A small tube made carefully by a laser. Even though it may help increase the clarity grade of the diamond, it may be noticeable in some diamonds when seen with a microscope. After the tube is made, an acid solution is then inserted into the hole, filling the small tube in with the solution. Laser drilling a diamond is irreversible.


Laser Identification:

A small inscription engraved by a laser in order to identify the gem.



Used to examine diamonds, the loupe is a small magnifying glass that is used universally by professional jewelers.


Marquise Cut:

The marquise cut is a type of cut that has a “boat-shaped” appearance. It has two curved sides along with two pointed ends. The marquise cut is named after Marquise de Pompadour, who is the mistress of King Louis XV.



A term used to define small diamonds less than .20 carats.


Mixed Cut:

The mixed cut is a combination of an emerald and brilliant cut. It contains the sparkle of the emerald cut with the gleam of the brilliant cut.


Mohs Scale:

The Mohs scale is a scale to determine the hardness of the mineral. It is determined by its ability to scratch other, softer diamonds. According to the scale, the diamond, being the hardest, is rated as a 10, while talc, being the softest, is rated as a 1.



Moisannite is a simulant or synthetic diamond that includes some properties of a real diamond. In order to detect fake diamonds, professional jewlers use a thermal probe. Seeing as the moisannite and the diamond has the same properties, moisannites might appear “real” or “authentic” to the jeweler. Even though both the moisannite and a real diamond both have the same thermal conductivity, the differences between the two are obvious to the untrained eye. Moisannites might appear slightly green or gray, because it is impossible to produce a colorless moisannite.



The part of the original surface of the rough diamond that is left on the polished stone is called natural. Even though naturals cannot be seen with the naked eye, some jewelers see naturals as imperfections.  It may be appear as blemishes or flaws on a diamond, while, according to others, it may be seen as a mark of a skilled cutter, trying to maintain the diamond’s original weight.



The needle is an inclusion in the shape of a tiny rod found within the diamond.



Usually found near the girdle, the nick is an imperfection on the diamond usually caused by a light blow. It is a gash on the diamond, which can also be found on the facet.


Off Make:

An off make is a term used to describe a horribly proportioned diamond.


Old European Cut Diamond:

Consists of a very small table, a heavy crown and large depth. It is one of the earliest versions of the brilliant cut.


Oval Cut:

The oval cut is a type of shape that has an elliptical form. It is another version of a round cut, but more elongated.



The pave is a type of jewelry setting in which small gemstones are mounted very close together to make a diamond crust to cover the metal underneath it. This is done to make the surface appear as if it is “paved” with diamonds.



The pavilion is the lower portion of the diamond beneath the girdle.


Pear Cut:

A type of cut that is similar to the shape of a teardrop or pear.



A pinpoint is a small inclusion within the diamond that can be seen as a small dot. A group of pinpoints are often called a “cloud” or “cluster”. This may be seen on the diamond as a hazy or grey area on a diamond.



A point is a term used to describe a 100th of a carat.


Polish Lines:

Miniscule parallel lines on the diamond left by polishing are called polish lines. They are caused by crystal structure irregularities.


Polish Marks:

Caused by excessive heat or uneven polishing, polish marks can appear on the surface of the gemstone, causing it to produce irregularities or defects on its surface.


Princess Cut:

A brilliant cut, which can either resemble a shape of a square or a rectangle, is a popular cut because of its ability to keep some of the sparkle found in the round brilliant cut of a diamond.


Prong or claw Setting:

The prong or claw settings are four to six claws that hold the diamond in place. This setting also allows the maximum amount of light to enter, resulting in a more brilliant reflection and shine.



An important element in gemstones, the proportion is the relationship between the angles of the facets of the crown and the pavilion.


Radiant Cut:

A type of cut that is shaped like a square or rectangle is called a radiant cut. This has a step cut and a scissor-cut on the crown and a brilliant cut on the pavilion.


Rough Girdle:

The rough girdle is a grainy, notched surface, often filled with nicks.


Round Brilliant Cut:

Containing fifty-eight facets, the round brilliant cut is the most common cut of diamonds. This cut is also considered the best cut to have, because of its ability to reflect light so well, adding brilliance to its fire.



The position of a diamond’s color on a neutral to vivid scale is called saturation.



Scintillation is the sparkling light that reflects from the facets of the gem. This light that flashes from the diamond usually catches the observer’s eye, adding extra gleam to its radiance.


Shallow Cut:

When a diamond has a shallow cut, the gem will lose light through the bottom, causing the diamond to not show its full brilliance through its reflection.



The shank is a part of the ring that fits around the bottom of the finger.



The outline appearance of the diamond is called the shape. Shapes include round, triangular, square, marquise, pear, oval or heart-shaped diamonds.



The term simulant is another word for imitation. It is made out of diamond like material that gives the appearance of a real diamond, but does not contain the characteristics of one.


Single Cut:

A very tiny round diamond that contains only sixteen or seventeen facets, instead of the normal fifty-seven or fifty-eight facets, found on a full, round cut brilliant diamond.


Star Facet:

Found on the upper crown section next to the table, the star facet is one of the eight triangular facets of a brilliant cut diamond.



Step cut diamonds include the emerald cut and the baguette cut diamonds. They contain rows of facets that resemble steps of a staircase.



The symmetry of a diamond refers to the arrangement of its facets and angles. Grading reports rate a diamond’s symmetry in terms of “excellent, very good, good, fair, or poor”. A diamond’s symmetry determines its ability to reflect light at its fullest.


Table Facet:

The table facet is the largest facet on a gemstone. It is located on top of the crown, making it possible for light to enter and reflect back.


Table Percentage:

The table percentage represents the value of the diameter of the table facet compared with the diameter of the entire diamond. In order to calculate the table percentage on a round diamond, gemologists divide the diameter of the table by the diameter of the girdle.



The tone is a characteristic of a color that determines the shading of the gem. It is based on a colorless-to-black scale.


Treated Diamond:

A diamond exposed to radiation in order to change its color is called a treated diamond. Other possible treatments on diamonds that can be considered “treated” are coating, fracture filling, electromagnetic conduction and whitening by extreme pressure and heat.



A trillion is a triangular, brilliant cut diamond with forty-four facets.


Twinning Wisp:

A small line that may be seen inside the stone is called a wisp. Even though this is due to an irregularity in the diamond’s crystal structure, it does not affect the clarity of the stone.



A naturally occurring metal, zirconium is widely known for its synthesized crystal form, cubic zirconia. Cubic zarconia is a simulant that is made out of diamond like materials but does not have the characteristics of one.