This cut was created by the Asscher family of Holland or, more specifically, Joseph Asscher - who was also commissioned to cut the world's largest diamond, the 3,106 carat Cullinan. Square in shape and step cut, the Asscher cut is sometimes known as a square emerald cut, although purists, including patent-holder the Royal Asscher Company, disagree with this.
The cut got its start as a modified cushion, but later was inspired by the table cuts used during the Renaissance period. Its unique appeal is said to be characterised by the feeling of vertigo or 'falling into' the stone that bestows a viewer. This opposes it to other diamond cuts, where the chief aim is to reflect light out of the stone.
The Asscher cut has no ideal proportions; however, a table of 65 per cent, depth of 70 per cent and wide corners will generally create the prerequisite vertigo effect - a windmill pattern from the wide radiating corners that taper right to the culet and small facet steps. Interestingly, in its experimentation with the Asscher, the American Gem Society found that an interesting pattern and excellent light return can be achieved with a 46 per cent table and 61.5 per cent depth.
With so many proportions and variables that work, creating an Asscher is part art and part science.
The best examples usually have a relatively high table and smallish spread. Technically, they should also be within about 5 per cent of being square. Asscher cut stones that are off square sometimes have a small keel or elongated culet like an emerald cut; arguably, these are square emerald and not Asscher cuts, even though they may still display the vertigo effect attributed to the Asscher.
Generally, original Asscher cut diamonds have three sets of crown and pavilion facets: 24 crown facets, 24 pavilion facets and one table facet making a total of 49 facets (with or without a culet). In 2001, the Royal Asscher cut was launched featuring 66 facets. A good yield from the rough comes from octahedrons that have one or two damaged or included corners. Like emerald and princess cuts, Asscher cuts also tend to show inclusions and colour more than round brilliant-cut diamonds.
Although the popularity of the Asscher cut is said to have hit its peak during the 1920s, it has enjoyed a considerable resurgence in recent years with younger women seeking to emulate the vintage glamour of this period.
As always in fashion, celebrities have been quite influential. Kate Hudson owns a 5-carat Asscher-cut diamond set in an Art Deco style ring by Neil Lane. Reese Witherspoon, another Neil Lane customer, owns a 4.5-carat stone. Sarah Jessica Parker's character, Carrie (from Sex and the City) was presented with an Asscher-cut diamond engagement ring by fiancé Aiden. Along with its vintage appeal, the cut also presents an alternative for clients who want something more unique than a princess or emerald-cut stone.
Clients that request an Asscher cut may also like a square emerald cut. Generally the latter has a cleaner bright brilliance, a larger table, smaller corners and a larger spread. In both cases, it is best to take care that there is a relatively thick girdle - at least medium - to provide optimum protection against chipping on the edges. This girdle tends not to negatively affect the appearance of the stone.
Asscher cuts make up only a small percentage of overall jewellery sales. They work well with shoulder stones in rings or in bracelets. For earrings and pendants, emerald cuts tend to work better than Asscher cuts because of their greater brilliance.