Cut

The cut of a diamond is, for most graders, the most important of the 4Cs. It defines not only a diamond’s shape but, more importantly, its brilliance and its fire. A cut is the sum of three things — proportion, symmetry and polish — and when all three are right, the diamond seems to capture light inside itself and never quite let it go.

Cut well, a diamond appears larger, brighter and more alive than its weight suggests. Cut poorly — too deep, too shallow, or carelessly finished — and light leaks out through the bottom instead of returning to the eye, leaving the stone dull no matter how fine its colour or clarity.

Ideal-cut diamonds

An ideal cut is proportioned so that the maximum of light entering the crown is returned through the crown to the eye, rather than escaping through the pavilion. Achieving the perfect brilliance of the round brilliant took decades of research — innumerable calculations of light refraction, dispersion and hardness — before the modern proportions settled.

Hearts & Arrows

Seen from above, a diamond of true optical symmetry shows an exact pattern: eight grey arrows face up, and eight grey hearts face down, visible through a special viewer. Hearts and Arrows is the ultimate expression of precise cutting — a near-perfect symmetry that only the most exactingly cut stones display.

Brilliance, dispersion, scintillation

A well-cut diamond exhibits three distinct properties:

• Brilliance — the white light returned to the eye from the surface and interior.
• Dispersion — the splitting of white light into spectral colours, the “fire” of a diamond.
• Scintillation — the flashes of light and dark that play across the stone as it, or you, moves.