|oblong cut octagon cut cubic, or isometric, crystal system|
|Written by Administrator|
|Friday, 21 September 2007|
oblong cut. Same as emerald cut. Occidental diamond. A misnomer for rock crystal.
Ocean of Light diamond. See darya
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).
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
octavo. Same as oitava.
Oda. The district in the Eastern Province of Ghana in which major diamond deposits are located. See
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).
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