oblong cut octagon cut cubic, or isometric, crystal system
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Friday, 21 September 2007

oblong cut. Same as emerald cut. Occidental diamond. A misnomer for rock crystal.

Ocean of Light diamond. See darya

l-NUR diamond.

octagon cut. An octagonal (eight-sided) form of cutting, usually step cut, the length and angles of the sides of which may vary.

octagon work. The operation of plac­ing the eight main facets on the crown and pavilion of a diamond, thus converting the table into an oc­tagon shape.

octahedral cleavage (ahk'-tah-he"-dral). Cleavage parallel to any of the four pairs of faces of the octahedron.

See OCTAHEDRON, CLEAVAGE, CLEAVAGE (IN diamond).

octahedron (ahk'-tah-he"-dron).

Octahedron


One of the seven basic (and the most common) forms in the highest sym­metry (hexoctahedral) class of the

cubic, or isometric, crystal system. It has eight equilateral, triangular faces, each of which intersects all three of the crystallographic axes at an equal distance from the center. See cubic

SYSTEM, HEXOCTAHEDRAL CLASS. (See

photos.)

octavo. Same as oitava.

Oda. The district in the Eastern Prov­ince of Ghana in which major dia­mond deposits are located. See

GHANA.

Oersonskraal. A minor alluvial dia­mond deposit in the Wolmaransstad area, Transvaal Province, Republic of South Africa. Approximately 700 carats were reported from this dig­ging during one recent year.

off-center culet. A culet that, due to differences in the angles of the op­posite pavilion facets, is off center with respect to the girdle outline. It usually results from repairing or re-


polishing a portion of the pavilion or from attempting to retain maximum weight from a distorted piece of rough. Off-center culets often result from pavilions at the same angles but of different sizes. See culet, closed

CULET, OPEN CULET, BRILLIANT CUT (ROUND).