Glossary - Rarity4u

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Glossary of antique and collectable terms

There are 856 entries in this glossary.

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O

Term	Definition
Object of Virtue	Virtue is about virtuosity, meaning exceptional technical skill in the fine arts, and implies a love and appreciation of such skills. So objects of virtue are not crucifixes or alter cloths but small precious objects, made using a variety of materials, and valued for both the technical skills they represent and for their beauty
Obsidian	Obsidian, also called Apache tears, is a volcanic glass that is usually black, but is occasionally red, brown, grey, green (rare), dark with "snowflakes," or even clear. This glassy, lustrous mineral is found in lava flows, and obsidian stones can be massive. Obsidian is formed when viscous lava (from volcanos) cools rapidly. Most obsidian is 70 percent silica. Obsidian has a hardness of 5
Ogee	A term used to describe an S-shaped double curve, particularly those on bracket feet as used on first class mid 1700's furniture
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 colour. Emeralds are frequently oiled to mask their many inclusions.
Old Mine Cut	Old mine cut is a term that refers to a brilliant cut in which the stone is cushion-shaped and has a high crown (the upper part of a gemstone)
Old Rock Turquoise	Old rock turquoise is an old Persian (Iranian) turquoise term for very high quality turquoise (sky blue, veinless turquoise that retains it colour).
Olive	Olive is a term that refers to a bead that is olive shaped (elongated). This term is mostly used in the USA
Onyx	Onyx is a semi-precious stone that is black and white, generally arranged in layers. It is a form of agate with parallel banding. This structure lends itself to cameo making. Onyx is a species of chalcedony (microcrystalline quartz).
Opal	Opals are semi-precious stones that are luminous and iridescent, frequently with inclusions of many colours ("fire"). Opal is a mineral composed of noncrystalline (amorphous) silica (and some water) and is a species of quartz. There are three major types of opals: common opal opalescent precious opal (white or black, with a rainbow-like iridescence caused by tiny crystals of cristobalite) fire opal (a milky stone that is firey orange to red in colour with no opalescence). Contra luz opals are transparent opals that show a brilliant play of iridescence only when light shines through the stone. Many opals have a high water content - they can dry out and crack if they are not cared for well (opals should be stored in damp cotton wool). Opals are found in many places worldwide, but Australia has a tremendous variety of beautiful opals. Opals have a hardness of 5.5 to 6.5
Opal Doublet	An opal doublet is a manufactured stone that is composed of two thin layers that are glued together. A thin layer of opal is glued on top of another mineral (usually a black onyx or ironstone, which enhances the stone's color), producing a stone that is less expensive than a solid opal. Doublets must be cleaned very carefully
Opal Glass	Opal glass is a milky white glass that mimics opals
Opal Triplet	An opal triplet is a manufactured stone that is composed 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. The clear quartz is the top layer, making the gem harder and less susceptible to scratches. An opal triplet is an opal doublet with a quartz layer on top. Triplets must be cleaned very carefully.
Opalescence	Opalescence is a milky white/blue type of iridescence
Opaque	Opaque means blocking the passage of light (as opposed to translucent or transparent).
Open Ended Necklace	An open-ended necklace has no clasp; it is worn by tying the ends together around the neck. Open-ended necklaces usually have ornaments, like beads or tassels, at the ends.
Open Setting	There are two basic types of gemstone settings: open settings and closed settings. Open settings are any type of setting that allows light to enter through the bottom of a faceted or transparent cabochon gemstone.
Opera Glasses	Opera Glasses are small decorative binoculars that became particularly popular in the 1800’s, as theatres and opera houses became larger. The high quality optical glass, originally developed for naval and scientific use, found a new application as a fashionable accessory. The best opera glasses were made in Britain, France and Germany.
Opera Length	An opera-length necklace is a single strand that is from 60 to 90 cm (30 to 35 inches) in length. Opera-length generally refers to a string of pearls that hangs to the breastbone.
Operculum	The operculum is part of many shelled animals - it is the calcified, disc-shaped "trap door" that opens and closes to protect the animal inside its shell. The operculum from a species of sea snail called the Turban Shell (Turbo petholatus, found in the South Seas north of Australia) is eye-like with a natural cabochon shape and is used in jewellery. This jewellery was popular in Victorian Era Britain. Operculum is also called Pacific Cat's-eye.
Ormolu	Ormolu (meaning "ground gold" in French) is an alloy of the metals copper, tin and zinc that is used to imitate gold. Ormolu can also be cast bronze or brass that is plated (gilded) with a gold and mercury amalgam, giving it a gold-like look. Bronze gilded by the Mercury or Fire Gilding process and used, especially in 1700’s and 1800’s France as decorative mounts. The term is also used for an 1800’s gold-coloured alloy of copper, zinc and tin. Ormolu mounts and object d' art were all the rage in French society of the 1700's, reaching a high water mark under the Imperial regime, and the ornament continued to be made and reproduced throughout the 1800's. British ormolu was never as fine as the best French products, but there is always a demand for French Style furniture, and ormolu is practically synonymous with this. Ormolu is used in frames, chandeliers, candlesticks, and furniture ornamentation. It was very popular in Georgian and early Victorian design. Ormolu can now also refer to any gold-like metal used as decoration. Ormolu is also called bronze dore or mosaic gold.