• Octahedron

    One of the most coveted crystal shapes for a rough diamond, with eight triangular faces that look as though two four-sided pyramids have joined together at the base.

  • Off-Make

    Trade term for a diamond that has been badly polished or finished. It has flaws in the overall make.

  • Old Mine Cut

    Diamond cut or shaped in an old-style cushion cut manner, with a deep pavilion depth, closed table, high crown height, and large facet on the culet.

  • Orange Diamond

    The ultimate colour for the collector, Orange is extremely rare in diamond. To be certified fancy orange colour, there cannot be any brown in the stone.

  • Oval Cut

    Diamond cut or shaped into an ellipse and covered with triangular facets in a brilliant cut style.

  • Over graded diamonds

    The practice of over grading the diamond to increase the perceived value. This practice is illegal. See link for more information. Rapaport.

  • Overblue

    Refers to a diamond that glows (fluoresces) strong blue under long wave ultraviolet light; in the past the term was used misleadingly to imply a diamond with superior colour. In fact, some diamonds with a high colour grade that have very strong fluorescence can look oily or milky under daylight.