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Oiling
A process of applying mineral oil
to a stone to enhance it and mask inclusions, make them more
transparent, and darken their color.
Old mine cut
A brilliant stone cut in which the stone is cushion-shaped and
has a high crown.
Onyx
A semi-precious stone that is black
and white in color and usually arranged in layers. It is a
species of chalcedony (microcrystalline quartz) and form of
agate with parallel banding.
Opal
Semi-precious stones that are
luminous and iridescent. Opal is a mineral composed of noncrystalline silica and is a species of quartz.
There are three major types of opals: common opal, opalescent
precious opal and fire opal. Opals have a hardness of 5.5 to
6.5and a specific gravity of 1.98-2.50.
Opal doublet
A manufactured stone that
is formed by gluing two layers together. A thin layer
of opal is glued on top of another mineral to produce less expensive
stone than a solid opal.
Opalescence
A milky white/blue type of
iridescence.
Opal Triplet
A manufactured stone made of three thin layers that are glued
together. A thin layer of opal is sandwiched between a layer of
clear quartz and a layer of either obsidian or ironstone.
Opaque
Blocking the passage of light, opposite to translucent or transparent.
Open – ended necklace
A necklace without clasp, it is
worn by tying the ends together around the neck. Open-ended
necklace usually have ornaments, like beads or tassels, at the
ends.
Opera-length
An opera-length necklace is a single strand that is from 30 to 35
inches (60 to 90 cm) long. Opera-length usually refers to a string of pearls that hangs to the
breastbone.
Oxidation
Oxidation is a chemical process in which
oxygen atoms bond to atoms of a material (like a metal) and
electrons are transferred from the oxided material to the reduced
material.
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