Glossary of Jewelry Terms
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Old-European Cut: A term applied to the earliest form of a circular, girdled
round stone or brilliant. It is characterized by a very small table, a heavy
crown, and usually great overall depth. Improperly referred to as an "old-mine
cut".
Old-mine Cut: (a) An early form of brilliant cut with a nearly square girdle
outline. (b) Incorrectly applied to a somewhat more modern style of brilliant
cut that also has a much higher crown and smaller table than the modern brilliant
cut, but whose girdle outline is circular or approximately circular—a
style of cutting that is more properly called a “lumpy stone” or
and old-European cut.
Onyx: A semi precious stone that is black or white in color lends itself to
flat jewelry creation such as cameos, since it has a layered structure. Onyx
belongs to the "chalcedony" family of minerals, which are somewhat
porous stones. It has a hardness of between 6.5- 7 on the Mohs Scale.
Opal: Opals, known for their iridescent, luminous qualities, are adored by
many. Opals contain a large amount of water and need to be cared for properly
since experts warn of potential cracking. This semi precious stone contains
a wide-ranging mixture of colors that produce a fire-like quality, which are
actually inclusions which can refract hues in a rainbow of colors. For more
information about the history of opals, visit Fabulous Facets Gem History (use
your browser's "back" key to return here)
Opaque (pronounced "oh payk"): Not transparent or translucent. An
opaque stone will not allow any light to pass through it.
Open Back Setting: Setting in which the back of the stone can be seen; if a
rhinestone, usually the crystal is unfoiled.
Opera Length: A necklace which is 48 to 90 inches long.
Ore: A metal bearing mineral from which metal can be profitably mined or extracted.
Oriental Pearl: A pearl that has formed naturally with no human intervention.
See also "Pearl".
Ormolu: A term referring to gilded bronze or brass mounts. From the French
for "ground gold"
Oval Cut: Faceted, elongated stone, round at both ends.
Oxidation: A chemical process in which a metal, such as silver, is blackened
or tarnishes, as a reaction to sulphur and oxygen.
Oxide: A compound containing one oxygen atom per molecule.
Oxidize: The act of combining with oxygen molecules to make an oxide.Oxidized
metal is rusted.
Oxygen: A nonmetallic element that is normally a colorless, odorless, tasteless
gas that constitutes 28 percent of the Earth's atmosphere. Oxygen combines
with many other elements easily. These compounds are called oxides and make
up about half the solid matter on Earth, making oxygen the most abundant element
present in the Earth's crust.
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