The practical history of diamond cuts can be traced back to the Middle Ages, while their theoretical basis was not developed until the turn of the 20th century.
The standard round brilliant is by far the most popular diamond shape. Shapes other than round are called fancy shapes. Fancy shapes have names of their own. The most familiar are the marquise, princess, pear, oval, cushion, radiant, heart and emerald cut.
The round brilliant cut diamond is by far the most popular and most researched diamond shape available today. For almost 100 years, diamond cutters have been using advanced theories of light behavior and precise mathematical calculations to optimize the fire and brilliance in a round diamond.The classic diamond is, to most people, a round gem of sparkling white brilliance with a kaleidoscope of dazzling facets to entice the eye.
The most popular of diamond cuts is the modern round brilliant , which facet arrangements and proportions have been perfected by both mathematical and empirical analysis.
The modern round brilliant consists of 58 facets; 33 on the crown (the top half above the middle or girdle of the stone) and 25 on the pavilion (the lower half below the girdle). The girdle may be frosted, polished smooth, or faceted. In recent decades, most girdles are faceted; many have 32, 64, 80, or 96 facets; these facets are excluded from the total facet count.
First introduced in 1960 by A. Nagy of London, It was originally intended for flat rough , but has since become popular enough that some gemological labs, have developed Princess cut grading standards with stringency akin to standards applied to round brilliant. The princess has pointed corners and is traditionally square in shape with many sparkling facets. Many princess cut diamonds are slightly rectangular. It is all about what you prefer in a diamond.
What makes this shape different is its pavilion, which is cut with rectangular facets to create a unique optical appearance. An antique style of cut that looks like a cross between an Old Mine Cut (a deep cut with large facets that was common in the late 19th and the early 20th centuries) and a modern oval cut. When selecting an emerald-cut diamond, good clarity and color are essential because inclusions and body color are much more obvious in this shape. Emerald cut diamond produces a hall-of-mirrors effect, with the interplay of light and dark planes. While less fiery, the long lines and dramatic flashes of light give the emerald cut an elegant appeal.