Jewelers Dictionary

Visit the Illustrated Dictionary of Jewelry
 

        

A                 

abraded culet

A chipped or scratched culet.  Can be caused by contact with another diamond.

abrasion

A bruise or scratch on the surface of a stone.

AGS

American Gem Society.  Professional organization formed in 1934 by several independent jewelers and the founder of the Gemological Institute of America (GIA).  The AGS is dedicated to setting and maintaining ethical standards and practices within the industry.

Antwerp

Perhaps the most noteworthy and versatile diamond-cutting center in the world.  All sizes and shapes of rough diamonds are cut in Antwerp. 

appraisal

A monetary evaluation, usually performed for insurance purposes by a gemologist.  Appraisals should describe the piece in detail, including color, clarity, proportions, stone sizes, flaws and other distinguishing characteristics.

B                 

baguette

A rectangular cut stone with squared corners.

bearding

Small feather-like cracks along the girdle of a diamond.

bezel

Outer ring of a watch case, usually designed to hold the crystal, that may also be used for advanced functions like diving timers.

bezel setting

Holds a gemstone in place on all sides at the girdle, creating a smooth, metal halo flush with the stone's crown.  Bezel settings often give the impression of a larger stone.

blemish

A flaw, spot or scratch on the surface of a gemstone.

blood diamonds

Information and answers about blood diamonds

brilliance

The intensity and amount of light reflecting from inside a diamond or gemstone.

brilliant cut

The most common style of cutting for diamonds and colored stones.  Brilliant cuts may be round or fancy and must have 57 or 58 facet cuts.

C                 

cabochon

A gemstone cut that creates a dome shape with no facets.

caliper

Instrument for determining the thickness or diameter of a gemstone.

carat

One of the "Four Cs".  Metric unit of weight for diamonds and gemstones.  One carat equals 200 milligrams or 0.2 grams.

certification

American Gemological Society (AGS), Diamond High Council (Hoge Raad Voor Diamant; HRD), European Gemological Laboratory (EGL), International Gemological Institute (IGI), and the Gemological Institute of America (GIA), to name a few.
 

clarity

One of the "Four Cs".  Measures the degree to which a gemstone is free from flaws.  A clarity scale is used to grade flaws in gemstones.  The scale ranges from FL (Flawless) where there are no visible internal or external flaws to I3, where many imperfections are visible to the naked eye.  

cleavage

Tendency of a crystalline material to break in certain directions, often along a grain or crystal face.

cloud

Group of tiny white inclusions in a diamond.

color

One of the "Four Cs".  In diamonds, the color scale ranges from D (colorless) to Z (yellow).  In colored gemstones, the grading scale differs widely depending on the type of stone.

comfort fit

Ring design in which the edges of the shank are rounded for maximum comfort.

crown

The facets or portions of a gemstone located above the girdle.

culet

A small polished facet located at the sharp point or base of a faceted diamond or gemstone.

cultured pearl

Pearls created by the artificial introduction of a mother-of-pearl irritant into an oyster or other mollusk.  Cultured pearls generally have thinner nacre and lack the luster of a natural pearl.

cut

One of the "Four Cs".  Perhaps the most important factor in determining the value of a diamond or gemstone.  The cut refers to the geometric proportion that dictates the reflection and refraction of light within a stone.  

D                 

depth

The distance from a gemstone's table to its culet (top to bottom).

depth percentage

The measurement of a gemstone's depth (top to bottom) in relation to its diameter.  Depth percentage is primarily responsible for refraction, which produces the fire or sparkle in a gemstone.

Diamond Gauge

A mechanical device used to determine the precise measurements of a gemstone.

DiamondLite

Instrument for color grading diamonds using visual comparisons to master diamonds.  Trademark, Gemological Institute of America.

dispersion

The separation of white light into the full color spectrum.  Often described as the "fire" or sparkle when discussing diamonds.

E                 

emerald cut

Step cut gemstone (most often rectangular) whose corners have been cut off.

extinction

Dark or black spots in colored stone.

eye-clean

Gemstone in which the flaws cannot be seen without a 10x loupe.

F                 

facet

Flat, polished surface or plane on a gemstone.

faceted girdle

Girdle that has been cut with facets.

fancy shapes

A gemstone shape other than round.

feather

Internal flaw (inclusion) that has a feathery appearance.

findings

Small, pre-fabricated parts of jewelry such as clasps, settings, etc.

fire

The sparkles of flashes of spectral colors emitted from diamonds and other gemstones.

flaw

General term used to refer to internal or external characteristics of a gemstone (i.e., inclusion, fracture, etc)

flawless

Term used to describe a gemstone that lacks discernable internal or external blemishes when viewed by a gemologist using no less than 10x magnification.

fluorescence

Luminescence that appears when certain diamonds are exposed to ultraviolet light.

fracture

Cracks, feathers or chips in a gemstone.

full cut

Gemstone with 58 facets.

G                 

gemologist

Gemstone specialist trained in gem identification, grading and appraising.

gemology

Science and study of gemstones.

GIA

Gemological Institute of America.  Non-profit organization specializing in grading diamonds and gemstones.  Widely held as the premier laboratory for gemological grading.

girdle

The narrow rim around a gemstone separating the crown from the pavilion.

gold

Gold, one of the most precious of metals, is virtually indestructible.   The karat mark on a piece of gold jewelry indicates how much pure gold that piece of jewelry contains.  The system of measuring with karats is based on a scale of 24, with 100% gold equaling 24 karats.  Since 24k gold is usually considered too soft to be used in jewelry making, gold is alloyed with other metals to strengthen and harden it. 

gold filled

Metal covered by a thin layer of gold that is at least 10k and 1/20th of the total weight of the piece

gold plated

Virtually the same as gold filled, except gold plated items may have a layer of gold that is less than 1/20th of the total weight of the piece

grading

Valuing a diamond using master stones.

H                 

head

Portion of a jewelry item that holds the stone.

I                 

imperfection

General term used to refer to internal or external characteristics of a gemstone (i.e., inclusion, fracture, etc)

inclusion

Visible internal flaws in a gemstone, including fractures, crystalling abnormalities, and foreign objects.

irradiation

Treatment performed on gemstones and even pearls to enhance color.

K                 

karat

Standard measure of gold purity.  One karat is 1/24th pure.

L                 

laser drilling

Technique used to enhance a stone's clarity by allowing for the introduction of bleaching agents or other enhancing agents.

leakage

Light leaving, or escaping, through the facets of fashioned gemstone.

Leveridge gauge

A millimeter gauge used to measure both mounted and unmounted stones.

loupe

Small magnifying glass, often held in the eye socket, used for analyzing gemstones.

luster

The appearance of a material's surface, as determined by the quantity and quality of light reflected.

M                

marquise

Oval shaped gemstone with ends sharpened to points.

master stones

A set of diamonds used to grade the color of other diamonds.

milgrain

Tiny beads of metal used to decorate bands of metal

Moh's Scale

Scale used to measure gemstone hardness.  Scale ranges from 1 to 10.

mounting

Method of holding gemstones in place (i.e., prongs, bezels, etc)

N                 

nacre

Crystalline substance that forms a pearl when secreted by a mollusk in response to an irritant.

O                 

off color

A stone presenting any semblance of undesirable color.

oiling

Temporary treatment used to enhance the color of a gemstone.

opera

A strand of pearls 32 inches in length.

P                 

pave (pah-vay') setting

Style of setting small stones as close together as possible.  Stones are set into drilled holes and metal beads are pushed over to hold the stone.

pavilion

The portion of a gemstone located below the girdle.

percussion mark

Indentation or bruise on the surface of a gemstone caused by contact from a pointed object.

pit

Indentation on the surface of a diamond or gemstone.

platinum

Platinum is pure, rare, eternal and versatile.  Platinum's purity endows it with a brilliant white luster.  This helps to reflect the true radiance of diamonds.  It is at least 95% pure and it does not fade or tarnish and keeps its look for a life time.  Platinum's purity makes it hypoallergenic and ideal for those with sensitive skin. 
 

plot

Diagram of a gemstone's clarity characteristics.  Generally performed during an appraisal using magnification.

point

One-one hundredth (0.01) of a carat.

princess

A strand of pearls 18 inches in length.

princess cut

Square cut, brilliant gemstone.

prong

Metal "finger" bent around the girdle of a gemstone to hold it securely in place.

proportion

Mathematical representation of a gemstone's overall symmetry.

R                 

re-cutting

Refinishing a polished stone in order to improve the stone's clarity, proportion or other imperfection.

reflection

Light rebounding off the polished surfaces of a gemstone.

refraction

Bending of light waves.  When white light is refracted, a full spectrum of color appears, as in a prism.

rope

A strand of pearls 40 inches in length.

rough

An uncut or unpolished diamond or gemstone.

S                 

setting

Method of holding gemstones in place (i.e., prongs, bezels, etc)

shank

Part of the ring that encircles the finger.

single cut

A simple form of cutting that has a table, approximately 16 facets and rarely a culet.

solitaire

Ring containing a single diamond or gemstone. 

symmetry

Uniformity of a gemstone's cut, including the shape and placement of facets.

synthetic stone

"Man-made" gemstone grown in a lab.

T                 

table

Largest facet on a gemstone.  The table sits atop the crown and allows light to enter and exit, creating the stone's brilliance.

table percentage

Diameter of a gemstone divided by the size of the table.

Tolkowsky, Marcel

Mathematician that defined the proportions necessary for maximum brilliance from a round diamond brilliant cut

U                 

ultrasonic

Cleaning device for jewelry that removes dirt through the use of ultrasonic waves.  Note:  Certain gemstones may be damaged by an ultrasonic cleaner.