- The large facet that caps the crown of a faceted gemstone. In the standard round brilliant, it is octagonal in shape and is bounded by eight star facets.
- Table Size
- The size of the table of a fashioned diamond, expressed as a percentage of the stone’s narrow-girdle diameter, is a dimension used in proportion analysis. On a round brilliant, it is measured from corner to opposite corner, rather than from flat side to flat side.
- Top Cape
- An early trade term still used by some dealers to designate the diamond color grade between crystal and cape in the river-to-light-yellow system. Small stones in this range will face up colorless when mounted, but larger stones will have a yellow tint.
- A triangular indentation occurring as a growth mark on diamond octahedron faces. The sides of the trigon are reversed with respect to the face on which it occurs.
- Twinning Lines
- Visible line on or with in a fashioned diamond, caused by twinning in the crystal. Since the orientation on one side of a twin plane differs from that on the other, the best polishing direction for one is a poorer one for the other; as a result, a line remains at the surface. Also called knot lines.