Blemish: A flaw (scratch or abrasion) on the surface of a stone.
Brilliance: White light reflected up from the surface of a stone. Brilliance is maximized by cutting a stone to the correct proportions.
Brilliant Cut: A 58-facet round stone.
Carat: A unit of weight for a stone, equivalent to 200 milligrams, or one fifth of a gram.
Clarity: A grade given to a stone to describe how many inclusions the stone has. The clarity scale ranges from FL (flawless), meaning a stone has no internal or external flaws, to I3 (severely included), meaning a stone has many flaws clearly visible to the naked eye.
Cloud: A cluster of small inclusions inside a stone.
Color: A grade given to a stone to describe the color tones of the stone. The color scale ranges from D, meaning completely colorless, to Z, fancy yellow. As the scale moves from D to Z, it indicates increasing levels of yellow and brown tone.
Culet: A facet on the very bottom of a stone. If the culet is medium to large, when the stone is viewed from the table, it will look like there is a hole in the bottom of the stone.
Cut: Commonly used to refer to both the shape of a stone (round, pear, oval, etc.) and the make (the exact geometric proportions to which a stone is cut). The make of a stone is the most important factor in determining how much sparkle comes from a stone.
Ideal Cut: Round stones that are perfectly proportioned (having depth percentages and table percentages that maximize fire and brilliance) and have high grades on polish and symmetry. These stones have had the finest craftsmanship to maximize the beauty of the stone.
Very Good Cut: Diamonds cut to fit very strict requirements for depth percentage and table percentage. These outstanding proportions maximize fire and brilliance in the stone.
Good Cut: Diamonds cut with acceptable, but not perfect, cut proportions. They generally have very good brilliance and fire and make excellent jewelry.
Fair Cut: Diamonds cut to less perfect proportions. They have been cut to maximize the weight of the stone, and sacrifice fire and brilliance. While less expensive than stones shown as having Good and Very Good cuts, they do not have the sparkle people expect from a stone.
Poor Cut: Poorly cut stones that look dead to the eye. These stones are not recommended for fine jewelry.
Depth: The height of a stone (measured from the culet to the table).
Depth %: The height of a stone (measured from the culet to the table) divided by the width of the stone. The depth % is critical to creating brilliance and fire in a stone; a depth % that is too low or too high will cause a stone to lack sparkle.
Eye-clean: A stone that has no inclusions visible to the naked eye.
Facet: The flat polished surfaces on a stone. A round brilliant stone has 58 facets.
Fire: Colored light reflected from within a stone. Fire is maximized by cutting a stone to the correct proportions.
Fluorescence: A glow, usually of a bluish color, which emanates from certain stones when exposed to ultraviolet light. Strong fluorescence should be avoided, but faint fluorescence usually does not affect the appearance of a stone.
Girdle: The narrow band around the width of a stone. The setting usually holds the stone around the girdle.
Inclusion: A flaw within a stone, such as a spot or irregularity in the crystal structure of the stone. Inclusions can either be visible with the naked eye (usually SI2 clarity and below) or visible only under magnification.
Make: The proportions to which a stone has been cut. A good make will have proportions that maximize the brilliance and fire of a stone. A poor make will lead to a stone that has little sparkle due to the inability of the cut to properly reflect light.
Pavilion: The bottom portion of a stone, from just below the girdle to the bottom.
Point: A weight measure equal to one one-hundredth of a carat. (A 0.50 carat stone is said to be 50 points.)
Polish: A grade given to the external finish of a stone. The polish scale ranges from poor to excellent.
Sparkle: The combination of fire and brilliance; the amount of light that reflects out of a stone.
Symmetry: A grade given to the overall uniformity of a stones cut. The scale for symmetry ranges from poor to excellent. Poor symmetry will hurt the sparkle of a stone. Diamonds with symmetry grades of good to excellent are recommended.
Table: The largest facet on a stone, located on the top of the stone facing out from the setting.
Table %: The width of the table divided by the total diameter of the stone. The table % is critical to creating sparkle in a stone; a table % that is too low or too high will cause a stone to lack sparkle.

J. Thomson Custom Jewelers
(A wholy owned subsidiary of Opals International Jewelrs)
5770 NW Expressway, Suite 101
Oklahoma City, OK 73132
(405) 495-6610 or
FAX (405) 728-1914
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