| 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. |
| 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. |
| 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
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 |
| IJO |
|
| 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 |
Precious
metal that is far harder than gold. Platinum does not tarnish and is
hypo-allergenic. |
| 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 |
| recutting |
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. |