|
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. |