Similar to the marquise, oval cut diamonds can display a bow tie effect: a dark area shaped like a bow tie in the centre of the diamond. The bow tie effect appears in some fancy cut diamonds such as marquise, hearts and oval cut diamonds. The bow-tie effect is caused by imperfect proportions between the height, length and width of the rough diamond from which the stone is cut. Due to this imperfect structure, light leaks through the diamond's pavilion, creating a dark shadow in the center of the diamond – from both girdles to the main belly facet. The effect creates an image that is similar to a bow tie, hence its name. The effect has varying levels, and is noticeable even without a magnifying glass. When it is very dark, the bow tie significantly damages the beauty of the cut diamond.

In short: The bow tie is a dark shadow across the centre of elongated fancy cuts — most visible in oval, marquise, and pear diamonds. It's caused by uneven pavilion light return and exists to some degree in nearly all elongated cuts. Aim for a faint bow tie (rated 'slight' or 'none') and a length-to-width ratio of 1.30-1.45 for oval. GIA does not formally grade the effect.

The Oval diamond one of the must popular diamond cuts nowadays is a beautiful brilliant cut diamond with a symmetrical elongated shape that gives an illusion of length on the hand, if worn on an engagement ring. It was created in the 1960s as an alternative to the round brilliant cut diamond.