Thought to have first appeared sometime in the 16th century, the cushion cut enjoyed tremendous popularity right through to the end of the 19th century.
At least part of the reason for the cushion's popularity during this period was that the technique for bruiting or rondisting rounds had yet to be either invented or perfected. As such, many diamonds of the Baroque period had cushion-shaped outlines.
Retaining yield from rough material was also a large part of the cushion's appeal; cutters could obtain a larger display cutting octahedra into a cushion, rather than a stone with sharp corners.
As well as old mine cuts, cushions come in two main styles: a brilliant style and a 'crushed ice' version. The latter is used to concentrate the colour in fancy-coloured diamonds by lengthening the ray path and reducing contrast.
There are many variants of the cushion cut but the most common versions today have 32 crown facets plus the table. It is the pavilion where the most variation occurs, as a guide: one variant has eight lower girdle facets, four main facets and six minor facets (between the main facets) making a total of 69 facets plus a culet. The pavilion facets in this example have more angle variations than a brilliant cut.
The shape of the corners may also vary greatly, from a curvature that is a pure radius to something more freeform. The amount of variation in this cut today is aided by the majority of shapes being planned digitally and then burned out of the rough with a laser saw.
Cushions are relatively easy to cut as standard diamond-manufacturing holders have eight-fold symmetry. It's a shape that is popular with diamond cutters because it offers great flexibility to achieve a high yield and a fair degree of control over the stone's visual effects.
Yet this flexibility also presents a number of challenges for the cutter. Because there are so many proportion variables, even a cutter who has produced a magnificent stone may not be able to replicate the same effect in a piece of rough that has, for example, a slightly different length and width ratio.
Such a degree of variation means that, unlike cuts like the princess or round brilliant, studying and optimising light performance in cushions has been challenging.
Variation also means that there are no true set ideal proportions for a cushion cut; however, as a general rule, a table could be between 55-62 per cent and the depth might be from 59-66 per cent.
A decision to purchase a cushion should never be based on a stone's proportions alone however; one should look at the diamond or use light performance tools like the AGS ASET scope.
The fancy-blue Hope diamond is cushion cut and arguably the world's most famous gem. In the last 100 years or so, other significant diamonds have also been cut into this shape: the Tiffany, the Rojtman, the Jubilee and the Red Cross.
In Hollywood, the cushion cut has found appeal with a number of celebrities including Sandra Bullock, Ashley Judd, Brittany Murphy, Anne Hathaway and Angelina Jolie.
Cushion cuts lend themselves well to drop earrings - where they can catch the light - or as centre stones, particularly in art deco or other antique styles. They are also particularly well-suited to stones that require a re-cut after an accidental chipping.