Briolette-Cut

A briolette has no table and no back. It is a teardrop faceted over its entire surface, so there is no single correct face-up view — it looks the same from every side, which is precisely the point for a stone meant to turn and swing rather than sit still in a ring.

That makes it earring and pendant material almost exclusively. Most are drilled through the narrow top to hang from a wire or a bail, so the stone moves freely and picks up light from whatever direction it happens to face. Standard millimeter sizes.