old-miner onza para diamantes CULET, BRILLIANT CUTopen setting
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Friday, 21 September 2007

old-miner. An abbreviated form of old-mine cut diamond.

old single cut. A simple form of bril­liant cutting that has a octagonal-shaped girdle outline, a table, 8 bezel facets, 8 pavilion facets, and sometimes a culet. Used for small Diamonds.

Ombelle M'Poko. A minor dia­mond-mining area in the Central African Republic.

one-grainer. See grainer.

onza para diamantes. Spanish, meaning the diamond ounce. Equal to 431.42 English grains.

onzuiver. A Dutch word meaning impure. It is used by some diamond men to refer to an imperfect dia­mond.

open cast mining. Surface mining, in which the ore (diamond for exam­ple) is exposed to the sky by remov­ing the overburden. All pipe mines are first worked from the top down­ward by this systematized method. The Finsch Mine is an excellent ex­ample of the open cast method of mining.

open culet. A culet that is larger than necessary; usually, one that is visible to the unaided eye. It may be de­scribed as medium, large or very large. See culet, closed culet, off-center


opening a diamond. In the dia­mond-cutting industry, a trade term used to describe the operation of polishing a facet, or "window," on the surface of a heavily coated or rough-surfaced diamond, so that a clear view of the interior can be had

by the cutter before proceeding with the work. A window must be ori­ented properly, so as to eliminate dis­tortion caused by refraction of light.

open setting. A stone setting in which the mounting holds a stone with the pavilion facets open to the light; effectively used with transpa­rent stones, especially diamond.

open table. A term that is sometimes used to refer to the table on a spread, or swindled, stone. To some, any table diameter of 60% or more of the girdle diameter is open; to others, open means 65% or more. See table;


Oppenheimer diamond. In 1964, Dutoitspan, the famed mine near Kimberley, South Africa, was the site of discovery of a large, pale-yellow octahedron. The Oppenheimer has only a few small black inclusions and is transparent and unusually well formed. It measures about 1% x VA inches and weighs 253.70 carats. In the same year, the owner, Harry Winston, New York City gem mer­chant, donated the superb crystal to the Smithsonian Institution,

Washington, D.C., in memory of Sir Ernest Oppenheimer, late Chairman of the Board of De Beers Consoli­dated Mines, Ltd. In 1971, it was dis­played at the "De Beers Hall" of the mining museum in Kimberley, Re­public of South Africa. Alternate name: Dutoitspan diamond.