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O Edit 14 terms found

O
A grade in GIA’s Color Grading System…. at the beginning of the “Very Light Yellow” category.
Octagon Case
A watch case having eight sides, shaped similar to that of a stop-sign.
Oersted
The centimeter-gram-second electromagnetic unit of magnetic intensity, equal to the magnetic intensity one centimeter from a unit magnetic pole. [After Hans Christian Oersted (1777-1851)]. The American Heritage Dictionary, Second College Edition. Copyright 1985 by Houghton Mifflin Company. All rights reserved.
Off Center Culet
This is a problem with the symmetry of a diamond… the culet is not lined up with the center of the table. The culet has been pushed over to one side of the diamond. It was intentionally done in order to repair damage to a previously polished diamond or from attempting to retain maximum weight from a distorted piece of diamond rough.
Off Make
A trade term for a poorly proportioned Diamond.
Officially Certified Chronometer
Around 1949, Rolex introduced this wording on the dials of their chronometer–rated models.
Oiling
Oiling infuses colorless oils, resins or waxes into tiny surface-breaking fissures to hide them and give certain gemstones a cleaner appearance. This long-practiced clarity enhancement is used mainly for emerald and jade. The oils used are either natural or have a natural counterpart. If coloring agents are added to the oil, the stones are classified as dyed rather than oiled.
Old European Cut
An early form of the Round Brilliant Cut diamond characterized by a small table, a high crown, deeper pavilion, and a large culet. Contrary to what you initially might have thought, it is not a diamond that was cut by an old European.
Old Mine Cut
A diamond cut that pre-dates the Old European Cut with the primary difference being the overall shape of the diamond was squarish…. similar to today’s Cushion Cut diamond.
Opaque
A term used for gemstones that you cannot see any light passing through the gem. Lapis and malachite are an example of this.
Open Table
A term that is sometimes used to refer to a diamond with a table of 65% or more.
Organic (gemstone)
Most gemstones are minerals with a crystal structure but some gems, such as amber and pearl, are organic rather than mineral, being formed by plants and animals. See also Amorphous gemstones.
Oval Cut
The famous diamond cutting house of Lazare Kaplan developed the Oval Shape Diamond in the early 1960′s. This is a brilliant style of faceting and is an elliptical variation of the traditional round brilliant cut.
Ovettone (or Ovetto, or Ovitone)
Italian for ‘little egg’, this nickname was associated with the Bubbleback models due to their rounded shape.