Diamond Cut

Cut describes how well a diamond's facets interact with light. It is assessed through proportions, symmetry and polish. A well-cut stone returns light through the table; a poorly cut one leaks it through the pavilion.

Three optical effects

Cut quality is experienced as a combination of:

• Brilliance — white light returned to the eye
• Fire — dispersion of light into spectral colours
• Scintillation — the pattern of sparkle as the stone moves

Fancy shapes

Laboratories issue overall cut grades for round brilliants. For fancy shapes, evaluate polish and symmetry grades, table and depth percentages, length-to-width ratio, and — most importantly — video of the stone in motion.