The threshold. Off-white stones carry the faintest cast, visible against a truly colorless diamond and invisible on the hand. The report notices. The eye does not. Set in warm metal, almost nothing of the look is lost.

Named for the way its facets open from a central point. Domed above, flat below, no pavilion and no culet. Cut since the sixteenth century and never about brilliance- it glows rather than flashes. The flat base gives it a broad face for its weight, and the shallow depth lets you see into the stone rather than off it.