Shapes of Diamonds - Pear Shape
The Pear cut is a tear-drop shape and is a variation of the round brilliant cut diamond. This attractive diamond is also extremely well-suited to pendants and earrings. Many of the largest stones ever discovered have been cut and faceted into magnificent pear-shapes.
A hybrid cut, combining the best of the oval and the marquise, it is shaped most like a sparkling teardrop
Length to width ratio: Most people prefer a pear-shaped diamond to have a length to width ratio of approximately 1.65:1. More elongated pear-shapes extend to a ratio of 1.80:1, whereas a more compact look is achieved with a ratio closer to 1.20:1
Shapes of Diamonds - Heart Shape
The ultimate symbol of love, the romantic Heart shape is a variation of the round brilliant cut diamond. This ultimate symbol of romance is essentially a pear-shaped diamond with a cleft at the top. The skill of the cutter determines the beauty of the cut. Look for a stone with an even shape and a well-defined outline.
Length to width ratio: A heart-shaped stone is usually proportioned with equal length and width, approximating a ratio of 1:1. A length to width ratio of between 0.90:1 and 1.15:1 is preferred. The ratio should not fall below 0.80:1 or exceed 1.20:
Shapes of Diamonds - Oval
The Oval cut is elliptical in shape and is a variation of the round brilliant cut diamond. The oval shaped diamond gives a flattering illusion of length to the finger and hand, and is popular among women with small hands or short fingers. It can also accentuate long, slender fingers.
Length to width ratio: An oval cut with a length to width ratio of approximately 1.40 - 1.60 is the preference of most diamond buyers. For those who prefer a rounder look, choose a ratio closer to 1.15:1. For those who prefer a more elongated shape, look for a ratio of 1.70:1
Shapes of Diamonds - Asscher The Asscher cut is a variant of the emerald cut and provides a uniquely regal and elegant look to its wearer. Its art-deco styling combines old-world charm with modern cutting and faceting techniques to produce a dazzling example of brilliance.
 Length to width ratio: Very Square Asscher cuts (Ratio of 1:1) are prefered to even slightly more rectangular looking ones. Asscher cuts should not exceed a ratio of 1.1:1.
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Shapes of Diamonds - Triangle / Trillion
This is a brilliant-cut triangle diamond - a wedge shape with fiery brilliance. It can be a traditional triangular shape with pointed corners, or a more rounded triangular shape. Trillions (also called Trilliants or Triangles) are often used as diamond accents in three stone rings and other jewelry settings, but may also be chosen to be set as solitaire diamonds.
This is a spectacular wedge of brittle fire. First developed in Amsterdam, the exact design can vary depending on a particular diamond's natural characteristics and the cutter's personal preferences. It may be a traditional triangular shape with pointed corners or a more rounded triangular shape with 25 facets on the crown, 19 facets on thepavilion, and a polished girdle. It is definitely for the adventurous.
Length to width ratio: An equilateral triangle is prefered in a trillion diamond. Variance in the ratio of length to width should not deviate considerably.
When purchasing an emerald cut diamond, it's extremely important to pay attention to quality and to select the 
The Cushion Cut has fewer facets than most other shapes and the facets are larger, so with this shape importance as inclusions will be more easily visible to the naked eye.