Hold the stone face-up under daylight, 25 centimetres from your eye. What you are looking for first is light: brightness, fire and the small flashes called scintillation. That is cut.
Turn it over on a white card. A colourless D diamond looks like water; by J, a warm tint appears along the pavilion. That is colour.
Clarity is about the tiny crystals and feathers inside. Most are invisible without a loupe. The fifth C is character — the reason you keep looking.
Two thousand hours for one wing
Why we love the garden inside an emerald