Professional Jeweler Archive: Face of a Diamond

March 2001


Face of a Diamond

The surface of a diamond crystal harbors clues about how it grew in nature

Gemologists sometimes say it’s a tragedy rough diamonds end up being faceted. Rough crystals, particularly well-formed octahedral crystals, are beautiful to behold because of their symmetry and interesting growth features.

Close examination reveals growth texture composed of triangular pits called trigons. Some are microscopic, others can be seen by the naked eye. They give a rough diamond an almost scaly, yet hard and slippery feel.

Trigons are growth (or lack of growth) manifestations of the crystal’s atomic structure. Diamond’s carbon atoms bond symmetrically, forming cubic structures, though the external shape can be cubic, octahedral, dodecahedral or variations of any of these.

Trigons always point in the opposite direction from the crystal face. “It is generally agreed that natural diamonds go through a multicycle processing in the earth before they are finally recovered through mining,” writes John I. Koivula in The Microworld of Diamonds (Gemworld International Inc., Northbrook, IL). “This processing includes initial growth followed by dissolution or etching. Some also believe that regrowth after the first stage of dissolution also occurs … a diamond may go through numerous growth cycles.”

A diamond’s face is made up of stacked crystalline layers that appear as step-like structures along the edges. These edges, which also point to the diamond’s planes of atomic weakness (its cleavage planes), are unique in nature. No gem crystal – natural or synthetic – even remotely resembles a natural diamond in its external appearance. For some that might be another good reason not to facet them.

An octahedral diamond crystal like this often shows eye-visible growth features called trigons. They always point in the opposite direction from the crystal face. The edges of diamonds often have unique step-like features. Diamond courtesy of Leo Schachter Diamonds, The Ideal Source, New York City; (800) 223-2082. Photo by Robert Weldon. The crystal face of the same diamond at 40X exhibits a regular arrangement of trigons. Photo by Robert Weldon.

– Robert Weldon, G.G.

Copyright © 2001 by Bond Communications