What cut is best for moissanite?

Moissanite has roughly 2.4 times the dispersion of diamond (0.104 against 0.044), which is what produces the bright rainbow flash. Cut shape decides how that fire is distributed. Large open facets, like those on a brilliant-cut oval or pear, throw bigger, more concentrated flares, which is what gives those shapes the "disco ball" reputation under sunlight. Smaller, more numerous facets break that light up into many tiny flashes that read closer to diamond scintillation. The geometry of the cut, not the carat weight alone, is what determines how diamond-like the stone reads on the hand.

Crushed-ice cushion and radiant cuts are the closest moissanite gets to a diamond look. The densely packed facets scatter light into smaller flashes that mimic diamond scintillation, and the slightly broken table reduces the central flash that gives moissanite away in photos. Round brilliant comes next: the pattern is bright but predictable and reads classic in any setting. Brilliant ovals, pears and elongated cushions show the most rainbow flash, especially above 1.5 carats. If you specifically want the moissanite look, a brilliant-cut oval or pear above two carats gives the biggest show.