Emerald cut

It is a step cut: a rectangle with bevelled corners and concentric rows of facets on both the crown and the pavilion. Long, open facets run parallel to the edges, which is why the stone looks like a clean frame inside a frame rather than a field of tiny sparkles.

The style was originally designed for emeralds, to reduce cutting pressure and prevent chipping, and it was later applied to diamonds. Compare the round brilliant, which is built for maximum brightness.

Step cuts have long, open facets instead of many small ones. The long rectangular facets make inclusions more visible than in other cuts, and the cut produces less scintillation, or sparkle, than other diamond cuts, which makes the diamond's colour more prominent. GIA also says step cuts tend to show colour and clarity more, while brilliant cuts are better at hiding them.

The practical result: a flaw that a brilliant would hide can be obvious in a step cut, and a faint yellow tint is easier to notice. The table sets the two cuts side by side.

GIA suggests choosing an emerald cut with VS2 clarity and G colour or above, and higher grades for stones of 2 to 3 carats or more. Treat that as a starting point to inspect from, not a rule: two stones with the same grade can look different, and a grade is a range. Look at the stone, ideally in daylight, and pay attention to where inclusions sit. Colour is less forgiving too: in a step cut, a body tint that a round brilliant would soften is easier to see.

The honest trade-off is that you may spend more on clarity and colour in an emerald cut and less on size, compared with a brilliant of the same budget. If you like the shape but want a more forgiving stone, the radiant cut, a mix of step facets on the crown and brilliant facets on the pavilion, can be more forgiving of inclusions.

GIA's buying guides give no preferred length-to-width ratio for emerald cuts, so choose the outline you like. The ratio is the long side divided by the short side, found in the measurements on the grading report.

For a good one, look for even corners, parallel sides and facets that line up evenly. GIA's advice for fancy shapes is to avoid uneven, narrow or missing corners and sides that are not parallel. There is no overall cut grade from GIA for this shape, only polish and symmetry, although AGS Laboratories says it has extended its cut grading to emerald cuts.

The angular shape suits designs from vintage-inspired Art Deco mountings to minimalist rings, and the stone can be set vertically or horizontally (east-west, across the finger). A solitaire or a three-stone ring both leave the long facets visible.

If you like step facets but want a squarer outline, look at the Asscher cut. Because step facets show inclusions and colour readily, any setting that shows the facets also shows the grade, so view the actual stone.

Because the shape depends so much on how it reads in person, a visit helps. Ask to see a few emerald cuts of different widths, in daylight if you can. A showroom lets you compare step and brilliant stones side by side, and a custom engagement ring can be built around the one you choose. You can browse engagement rings to see existing styles first.