An Emerald Cut diamond is a diamond that has been cut to a rectangular or square step cut with diagonally cut corners. It usually has 2 to 4 rows of parallel facets to the center of the stone. A very popular style of cut used for Emeralds since the name. What makes this cut unique is the large flat face (table) when viewed from the top.
This flat face highlights the clarity of the diamond so only high quality diamonds are cut to this shape. The shortage of impurities and inclusion in the stone will increase the price so emerald cut diamonds are usually more expensive than other cuts with the same caret weight.
The classic emerald-cut shape has a length to width ratio of 1.30 to 1.40. It is interesting to note that studies done back in the mid 1970s showed that the majority of successful business also had logos with the same length to width ratio. Other length to width ratios is available and if they are pleasing to the eye is determined only by individual tastes. 1.25, 1.50, and 1.75 are very common and if you prefer a more square shape then take a look at the Asscher cut. It also has a flat face to highlight the clarity of the diamond but has a length to width ratio of about 1.0 to 1.05.
When purchasing an emerald cut stone of SI clarity grade or lower, be sure to review the clarity plot on the diamond certificate. A diamond is said to be Slightly Included (SI1 to SI2) when it presents defects that are easy to locate under 10x magnification.
The Darya-I-Nur diamond is one of the most famous emerald-cut diamonds in the world. It is also believed to be the largest pink diamond in the world. The stone is estimated to weigh somewhere between 175 and 195 carats, and it is a light pink color. Its exact weight is not known because its been mounted in its brooch setting for over 130 years. This stone is one of the most celebrated diamonds in the Iranian Crown Jewels and it is also one of the oldest stones known to man.
Source by David Cowley