Obsidian

Obsidian is a rock which is a type of naturally occurring glass, produced by volcanoes (igneous origin) when a felsic lava cools rapidly and freezes without sufficient time for crystal growth. Sometimes it is called volcanic glass.
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Off-loom

Off-loom bead weaving is a family of beadwork techniques in which beads (typically seed beads) are woven together into a fabric or a three-dimensional object such as a beaded bead (or beaded ball), clasp, or a box. Off-loom bead weaving encompasses a number of techniques, including:

• Gourd Stitch or Peyote Stitch
• Brick Stitch
• Square Stitch
• Right-angle Weave
• Triangle Weave
• Bead Netting
• African Helix
• Dutch Spiral

Oiling

Oiling is a process of applying mineral oil to a stone in order to enhance it and mask inclusions, make them more transparent, and darken their color.

Olivine

Another name of chrysolite, or peridot. It ranges in color from a light pea green to a deep olive green and an oily shine. Also called night emerald.

Omega

Flat chain with a solid surface formed by the links and worn high on the neck.

Onyx

Onyx is a banded variety of chalcedony, a form of quartz. The colors of its bands range from white to almost every color (not including shades such as purple, blue, or black).
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Opal

Opal is a mineraloid gel. There are a lot of kinds of common opal such as the milk opal, milky bluish to greenish; resin opal, honey-yellow with a resinous lustre; wood opal; menilite brown or gray; hyalite, a colorless glass-clear opal; geyserite; and diatomite. Precious opal shows a variable interplay of internal colors and does have an internal structure.
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Opalite

Opalite is not a gemstone, it is a high quality glass with an infusion of milky opalescent. Against a light background, it is milky white and has golden highlights mixing with faint lilac-blue and other colors around the stone.

Opaque

"Opaque" and "opacity" are terms used in various contexts to describe something that is not transparent. Light cannot pass through an opaque bead because opaque beads transmit no light. You can't see the thread in an opaque bead.

Opaque Matte

They are the same as opaque beads (light does not pass through), but with a dulled or non-shiny surface.

Open-ended Necklace

An open-ended necklace has no clasp; it is worn by tying the ends together around the neck.

Opera Length

An especially long strand necklace. Length is 26 inches to 36 inches.