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GLOSSARY OF FREQUENTLY USED
++As I was trained in
grading and describing colored stones by GIA, many of these
definitions are similar to or identical with theirs - some, however;
are my own as are any errors herein.++
Flawless at 10x:
using a 10 power magnifier and good light, no inclusions, surface
imperfections or color banding can be seen.
Internally flawless: using a 10 power magnifier and good light, no inclusions
can be seen, but there may be polish marks or tiny abrasions on the
surface. "Almost "or "nearly" used with either of the above means
that only the tiniest imperfections can be seen.
Darkfield illumination: a way of lighting a gem so that normally hard to see
inclusions stand out sharply in relief. I use this lighting in
conjunction with the 10x loupe in grading the stones.
stone has no visible inclusions, surface imperfections or color
banding as viewed face-up, about 12-16 inches away in normal, good
lighting. This is how the average person would view a stone in
jewelry or a collection . For many, this is the most desirable
clarity state as the stone looks great, but when viewed under
magnification shows internal characteristics which can prove its
naturalness or even identify its source. Since everyone's visual
acuity is different there's a possibility that what I label as
eyeclean might look better or worse to you. An eyeclean stone as
described above might have visible inclusions if scrutinized under
very bright light, held close to the eyes or turned on its side or
back where reflections do less to hide inclusions. "Better than" or
"almost" will be found as modifiers to the term eyeclean to indicate
stones which fall just outside this designation. In some gem pictures
which were taken with a magnifying closeup lens, inclusions may be
visible in the photo even though the stone is graded eyeclean.
Very Slightly to Slightly
Included: Stones with this designation have
eye-visible inclusions which do not markedly affect either the
stability or beauty of the stone. A few varieties such as emerald and
rubellite almost never exceed this grade.
Moderately Included: The inclusions are grossly visible and affect the beauty
and/or stability of the stone. Usually these stones are acceptable
only if the material is very rare or the price is very low.
much like driveway gravel. None are offered on this site.
**(colors usually are relative to the
range for that variety: a medium aqua would be lighter in tone than a
medium rhodolite, for example)**
AAA: the best
color that a stone could have for its variety. In the GIA scheme:
AA: just one shade
lighter or darker or one hue off the AAA color. 8-9/10.
Very dark: the
stone looks black under most lighting conditions, only in strong
sunlight or when lighted from the side or below is color seen.
Dark: the darkest
shade of color without looking black under normal lighting.
Medium dark/medium: these are the tone values which, for most stones, are
Medium light: not
as dark as medium, but with good noticeable color
Pale: only the
faintest hint of color, often only noticeable against a white
Intense/vivid/electric/neon, etc. Terms meant to indicate a richness of color that is
term means a color is pure, rather than being modified by grayish or
brownish tones. It is NOT a synonym for deep or dark. A stone can be
deep, but not saturated and saturated without being dark.
Usually this means a stone has been cut at the country of origin by
lapidaries working on native style equipment. Generally the stones
are windowed (to save weight) and often have little crown and very
large bellies (which deepens color). Often facet meets and polishes
are imperfect. Styles are usually ovals or cushions. On this site
"native cut" will mean a stone with these characteristics, regardless
of where it was cut or with what style of equipment.
Custom cut: This
means that a stone was cut using optimal pavilion angles to maximize
brilliance. It shows excellent symmetry, a well proportioned crown,
good facet meets, a fine polish and no window. Occasionally a custom
cut stone is deliberately windowed to show inclusions (rutilated
quartz) or to emphazise color separation (ametrine) or to lighten a
dark stone (almandite/iolite) In these cases, however, something
other than maximum brilliance was being sought. Sometimes stones from
"native" sources meet or come very close to custom specifications, in
which case they have not been designated as native cut. All gems, on
this site unless otherwise labelled are custom cut.
a stone is well proportioned if its crown is 1/3 - 1/4 of total
depth, and if its table falls between 40 and 70% of the total
Window: A window
is an area under the table of a stone that does not reflect light.
It's called a window because light goes through it like window glass.
It is almost always undesirable and occurs when pavilion facets are
cut below the critical angle for a gem material. To test for a
window, hold a gem, face up, with the table parallel to a sheet of
newspaper and look through it. If you can read the print, the stone
has a window. Most native cut stones have large windows as using low
pavilion angles allows a larger stone from a given piece of
Barion cut: A
style of cutting transparent stones invented by famed diamond cutter
Basil Watermeyer and named for Basil and his wife Marion by Glenn
Vargas. In essence, it's a way to bring the benefits of brilliant
cutting to shapes which are usually step cut. All the pavilion facets
are near the optimal angle for the gem so that maximum brilliance is
obtained. Frequently the crowns of such stones are step cut. The
pavilion is slightly deeper than most other cuts of the same face up
dimensions, a fact which should be taken into account when planning
to set the gem into a commercial mounting.
Apex: Instead of
a flat table on the crown of a stone, there is a low angle dome. It's
done to enhance interest, or to increase face up brilliance in a
species with a low refractive index.
Buff Top: a
style of cutting in which the pavilion is faceted and the crown is
Opposed Bar: a
style of crown with a series of parallel rectangular facets in place
of a table and other crown facets.
facets that, rather than being flat, are actually depressed or sunken
in. A special faceting machine that uses cylindrical cutting and
polishing laps is necessary. Such facets can enhance brilliance
and/or create interesting reflective patterns in the stone. Stones
cut this way are generally more costly than comparable stones with
regular faceting as the process is more time consuming and the
necessary equipment is more expensive.
Terms used to describe
Antique/Vintage and Estate Jewelry:
Antique: 100, or more, years
Vintage: The use of this term varies
widely, but on this site it will be used to designate pieces more
than 50, but less than 100, years old.
Estate: Estate items are previously
owned, and range from contemporary to 50 years old.
Victorian: 1837 - 1901
Art Nouveau: 1890 - 1915
Art Deco: 1920 - 1935
Retro: 1935 - 1950
Index: (RI) is the
characteristic slowing of light as it travels through a given gem
species. The higher the RI, the greater brilliance and luster is
possible. The fact that each gem material has its own RI makes it
necessary to facet each species at slightly different angles and
makes it a useful characteristic in gem identification.
Dispersion: The measure of a gem's ability to break
white light into spectral colors. The term "fire" is often used as a
synonym. Certain cutting styles, like high crowns can enhance
dispersion. Rich body color in a stone can sometimes mask some or all
of the dispersion, as in the case of Benitoite and demantoid
Luster: The ability of the gem's surface to
reflect light and the characteristic appearance of that light.
Adamantine luster (diamond-like) is generally considered the most
desirable. Most gems have vitreous (glass-like) luster; although
other possibilities range from metallic to greasy to dull. The luster
on a given gem is partly due to its nature and partly due to the
degree to which it has been polished.
Brilliance: The percentage of the total face up area
of the stone which is reflecting light back to your eyes as you rock
and tilt the stone. Brightness, sparkle, and light play are similar
in meaning; fire, though sometimes misused to mean brilliance, is
more properly used to describe dispersion. Well cut gems of light to
medium dark colors will generally show at least 60% brilliance.
Windowing (light passing through without being reflected) and
extinction (retention of light within a stone) subtract from the
potential brilliance. Poorly cut stones are often windowed and very
dark stones can show near total extinction. Inferior polish or
inclusions in the stone can also decrease brilliance.
The effect of reflected light being broken up into small patches
which seem to "twinkle" as the stone is moved. This is mostly a
function of faceting style. Brilliant cuts and many small facets
produce more scintillation, large facets and step cuts
Pleochroism: The characteristic of a given gem species
of showing a different color, or a different shade of the same color
through different angles of view. Dichroic stones, like ruby, show
two (orangey red and purplish red) and trichroic stones, like iolite,
show three (blue violet, grey and near colorless). This property is
useful in gem indentification. Pleochroic stones must be carefully
oriented by the cutter to show the most desirable color, or blend of
colors in the face up gem.
Particolored: The property of
showing two or more colors in a single piece of gem material, for
example, ametrine. Traditionally such stones have been cut to
separate the colors, but it's becoming more common to deliberately
orient the rough to mix the colors, or create a mosaic of them in the
finished stone. When a stone is cut in this matter it is called
Opalescence: An effect of slight milkiness due to
light scattering, seen primarily in transparent opals.
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