Diamond Glossary

Abrasion- many tiny nicks along the facet junctions of a diamond.  It gives the facet edge a fuzzy appearance. 

AGS- American Gem Society is a diamond and diamond jewelry trade association started in 1934.  AGS was created to establish a high standard of business professionalism and ethics in the diamond and jewelry industry.  They have become a worldwide authority in diamond grading.  Moreover, AGS has its own cut, color, and clarity standards. 

Appraisal- a written document stating the replacement value placed on an item.  This is a document usually for insurance purposes and will clearly state what the item is along with a picture of the item.    

Asscher Cut Diamond- this beautifully unique diamond shape looks like the emerald-cut, except it’s square. The pavilion is cut with rectangular facets just as the emerald-cut is. 

Average Girdle Diameter- the median of two measurements going across a diamonds outermost edge or girdle outline. 

Baguette- a rectangular step cut diamond, usually used as side diamonds on a diamond ring.

Belly- the ever-so-slightly curving at the center of the long side of an oval, pear, marquise, or heart shape diamond. 

Blemish- a clarity imperfection that’s on the surface of a diamond. 

Bow-tie- the dark area in the middle of some brilliant cut diamonds that literally looks like a bow-tie.  This usually happens to pear, marquise, heart and oval shape diamonds that are very shallow or very deep.  

Brilliance- the brightness created when light enters through the table of a diamond, reaches the pavilion facets, and is then reflected back out through the table, where the light is then visible to the eye.  Other gemstones display brilliance as well, but none equal a diamond's light-reflecting power. 

Brilliant Cut- a round cut diamond with 57 or 58 facets mathematically calculated to produce the greatest brilliance. 

Carat-. a unit measurement for diamonds and other gemstones.  One carat is equal to 0.2grams.  The abbreviation for carat is ‘ct’.   Each Carat is divided into 100 parts called 'points,' therefore, a 1-carat diamond has 100 points, a ¾ carat has 75 points, etc.   

Carbon Spots- a misnomer used  in the diamond industry to describe the appearance of certain inclusions in a diamond. 'Carbon spots' are actually included crystals with a dark appearance, rather than a transparent appearance, when viewed under a microscope. 

Certificate- a guarantee by an independent gemological laboratory that the diamond is indeed of the quality the seller represents. Diamonds are certified by independent gemological laboratories, skilled gemologists use specialized equipment to measure and evaluate each diamond's particular characteristics and attributes. 

Color-the less color in a diamond, the more rare the stone is.  Most diamonds fall into a category from colorless to light yellow and brown.  Aside from fancy colors (red, pink, green, etc.) the ideal color for a diamond is absolutely colorless.  

Color Grade – one of the 4c’s of a diamond.   Diamonds color is graded on a scale from "D" (colorless) to "Z" (noticeable tint of color, typically yellow or brown). Diamonds that are yellower than "Z" color are considered Fancy Colored Diamonds, they are graded different.     

Clarity- a quality of a diamond relating to the existence and visual appearance of internal characteristics called inclusions, and surface defects called blemishes.   The FTC requires all diamond grading be done under 10-power magnification; any flaws not detected under this magnification are considered non-existent. 

Clarity Enhancement- a diamond that’s been treated to improve its clarity grade by way of fracture filling, lasering or any other technique to eliminate inclusions. 

Clarity Grade – one of the 4cs of a diamond.  A diamonds clarity grading scale ranges from the highest grade being flawless(no inclusions visible under 10x magnification) all the way to included (eye visible inclusions). 

Cloud-many small included crystals together giving a hazy appearance. 

Crown- the upper part of a cut gemstone, above the girdle. The table, star, bezel, and upper-girdle facets all make up the crown. 

Crown Angle- an angle formed by the girdle plane and bezel facets. 

Crown Height- a measurement for the distance from the girdle plane to the table.  

Crystal-  a type of inclusion found in diamonds.  A crystal is a mineral deposit that has been trapped inside the diamond while the diamond was forming in the earth.  Location and size of the crystal may have a significant impact on the diamond's value. 

Culet-  the point on the bottom or pavilion of the diamond.  On some diamonds, the culet is actually formed into a facet; on others, it is formed into a point. This is why round brilliant cut diamonds will have either 58 or 57 facets, depending on whether the culet has been faceted or not. 

Cushion Cut- a faceted square or rectangular cut with cushioned or curved corners, this shape of diamond looks like an old mine cut .

Cut-  the geometric proportions to which a diamond is crafted by a master diamond cutter.

Depth- the distance from the table to the culet, measured in millimeters.

Depth Percentage-  the ratio of the total depth of the diamond (from table to culet) as compared with the average girdle diameter. So, if the average girdle diameter of a round diamond is 6.50 mm and the total depth is 4.00 mm, then the depth percentage is 61.5%.

Diamond - A mineral that crystallizes in the cubic system and is made of carbon with a hardness of 10, a refractive index of 2.417, and a specific gravity of 3.52.

Diamond Simulant- any material or stone that imitates a diamonds appearance and is used as a substitute.

Emerald Cut Diamond- a shape of diamond characterized by a rectangular shape and cut corners.  An emerald cuts facets are rectangular and trapezoid.

European Gemological Laboratory- Widely respected independent diamond grading lab.  One of the oldest laboratories in the diamond trade.

Eye-Clean- this term is used for a diamond that has inclusions which can only be detected with a jewelers loupe.

Eye-Visible- a diamond that contains an inclusion which is visible to the unaided eye.

Facet- flat polished surfaces on a diamond that provide the views of fire and brilliance.

Faceted Girdle- a diamond girdle with polished facets going around its circumference.

Fancy cut- any diamond shape other than round.

Feathers- tiny fractures in a diamond that were as a result of the stress while the diamond was underground forming.

Fire- describes the flashes of color coming from a diamond.

Flaw- an imperfection in a diamond

Flourescence- some diamonds will emit a visible light when exposed to ultraviolet radiation.  This light emitted is usually blue, yellow or white and will be noted on the diamond certification.

Four C’s – the four value factors for a diamond; color, clarity, carat weight and cut.

Fracture- a break or a chip on a diamond.

Fracture Filling- a diamond treatment involving a molten glass substance being injected into the surface of the diamond to improve clarity.

Full Cut Diamond- a round brilliant cut diamond with 57 or 58 facets.

Gemological Institute of America (GIA)- the largest diamond institute in the world and the creators of the “4c’s”.  A GIA diamond grade certificate is the most respected and recognized in the diamond industry.

Girdle- the part of a diamond that separates the crown from the pavilion, it’s the outer edge of the diamond.

Hardness- a measurement of how a diamond or gem resists scratching.  Mohs scale of relative hardness consists of 10 minerals, each mineral being able to scratch all those below it in scale and also be able to be scratched by all those above it.

Heart-Shape- a fancy cut diamond faceted to look like the ever romantic Valentine’s Day heart.

High Pressure, High Temperature (HPHT)- the process of changing a diamonds color with the use of special equipment and certain conditions.

Ideal Cut- a diamond that is cut to such precise proportions that the light entering through all sides of the stone, is sent back out through the table with maximum reflection and refraction.

IGI (International Gemological Institute)- an independent diamond grading laboratory based in Antwerp, Belgium. 

Inclusion- an imperfection enclosed in a diamond or going into it from the surface.

Irradiated Diamond: a diamond which has been exposed to radiation for the purposes of changing its color.

Laser Drilling- using a laser to eliminate or disguise inclusions in a diamond.

Length-to-width ratio- the relationship between the length and width of a fancy cut diamond.

Loupe- a small tubular magnifying glass used to view diamonds and other gemstones, usually 10x-magnification.

Marquise- a diamond cut in an elliptical shape with two pointed ends.

Melee- this term is used for diamonds under 0.20ct.

Old European Cut- this is an antique diamond cut first started in the 1800’s, long before today’s modern technology produced precise and geometrically perfect diamond shapes.  A descendent of the old mine cut diamond, European cut diamonds have a very small table and a bulky crown. This type of diamond is usually very deep, and the culet is usually larger than in contemporary cut diamonds. The overall shape of an Old European Cut Diamond is round, though some European cuts may be slightly oval due to the lack of technology used to cut diamonds generations ago.

Old Mine Cut – is the earliest form of the "brilliant cut" diamond, the old mine cut diamond is square with rounded corners and "brilliant" style facets. The crown is usually tall and the culet is usually large enough to be seen through the table.

Oval Cut Diamond- a diamond cut in an oval or elliptical shape.

Pavilion- the portion of a diamond below the girdle.

Pavilion Angle- the angle formed by the pavilion and girdle plane.

Pavilion Bulge- when the pavilion facets of a diamond bow outward.

Pavilion Depth Percentage- Average pavilion depth relative to average girdle diameter of a diamond. Pavilion depth is measured from the top of the pavilion main facet to the culet.

Pear Shape- a faceted diamond with the girdle outline in the shape of a pear or tear drop.

Perfect - The Federal Trade Commission considers it illegal to use the word "perfect" as a description of a diamond with inclusions that are visible to the naked eye.

Point- a diamond’s weight measurement, this term is used in the diamond trade;  1/100 of a carat.  So, 0.50 carats is equal to 50 points.     

Polish- the condition of diamond facet surfaces.

Princess Cut Diamond- a brilliant cut square or rectangular in shape.

Radiant Cut Diamond- a brilliant cut, square or rectangular diamond with the corners cut off.

Reflection- is when light bounces off of a diamond’s surface or any other surface for that matter.

Refraction- is when light bends as it travels through a diamond or any other surface.

Round Brilliant Cut- a faceted round diamond with 57 or 58 facets.

Scintillation- a diamond’s light flashes in contrast to its dark parts as it is tilted one way or another

Shape- the overhead view or face-up outline of a diamond is its shape. 

Single Cut Diamond- a diamond with a table, eight crown facets, eight pavilion facets and occasionally a culet.  This is an older cut diamond.

Symmetry- the placement of a finished diamond’s facets and look of the overall shape.

Synthetic Diamond- a manufactured stone with the same chemical, physical, and optical properties as a natural diamond.

Table- a diamonds polished surface on the top and center of the crown.

Table Percentage- the measurement of a diamond table in relation to its average girdle diameter.

Trillion  - a triangular faceted diamond.  The trillion has 25 facets on the crown and 19 facets on the pavilion.

Ultraviolet Light - Light with wavelengths shorter than those of visible light.  Thus, the light is invisible to the naked eye.