They are called drop cut or teardrop diamond.
A pear shaped diamond, also known as a teardrop, is popular not only as the center stone in a ring, but also as the focal point of a diamond pendant. An expert diamond cutter will ensure that light is reflected evenly throughout the stone. The cushion shape (also sometimes known as a pillow cut) was the most common diamond cut from the mid-19th century onwards. In today's market it's a rare cut and sought after by those seeking an unusual alternative to an oval shape. The cushion cut is available in square and more rectangular dimensions. The teardrop shape has a round or oval shape on half the facet pattern while the other half resembles a marquise with the sides tapering to a point. Some of the world's largest and most famous diamonds were cut in to the pear shaped brilliant cut. In the pear brilliant, as with marquise shapes and other elongated fancy shapes, there is an increased likelihood of having a bow tie.. This is a dark area in the shape of a man's bow tie that occurs when the angles of the cut are not optimum. Often called a teardrop diamond, the pear-shape diamond combines, at one end, the brilliance and facet similarities of an oval-cut diamond, and, at the other end, the strong shape of a marquise diamond. In essence, one end is rounded and the other is pointed. The pear-shape diamond weighs 67.89 carats and is a champagne color. It’s believed that the rough diamond from which it was cut weighed an astonishing 240 carats. It was first cut into a 75-carat pear shape and then re-cut into the 67.89-carat size to improve its brilliance. The pear shape is a combination of the round and marquise brilliant cuts and usually has the 58 facet brilliant pattern, but can be cut with different numbers of pavilion mains of 8, 7, 6, or 4 facets. In the pear brilliant, as with marquise shapes and other elongated fancy shapes, there is an increased likelihood of having a bow tie.. This is a dark area in the shape of a man's bow tie that occurs when the angles of the cut are not optimum. The pear shaped diamond and sapphires used in this ring are a somewhat different shape than the fatter pear shaped diamond on page 4, a difference that is also true for many other shapes.  A diamond cut is a style or design guide used when shaping a diamond for polishing such as the brilliant cut. Cut does not refer to shape (pear, oval), but the symmetry, proportioning and polish of a diamond. The cut of a diamond greatly affects a diamond's brilliance; this means if it is cut poorly, it will be less luminous. 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. Emerald cuts are sleek and elegant. The Emerald cut is rectangular with cut corners. 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. Diamonds are cut in many different and exciting shapes. The shape of a diamond is often confused with its cut. Shape refers to the basic form of the diamond: round, emerald, oval or pear shaped, for example. Cut or proportions refer to the ability of each of these diamond shapes to reflect light. Oval shape diamonds are also popular because their length can help create the appearance of long, slender fingers. With Oval shape diamonds avoid what is called a Bow Tie effect, a very noticeable darkened area in the shape of a bow tie towards the middle of the Oval cut diamond. Pear Cut Diamond. Exuding elegance, the pear shape diamond (also referred to as a drop cut or teardrop diamond) is cut to resemble a drop of water with a single point and rounded end. The result is a cross between a round and marquise cut. Learn more about Pear Cut Diamonds. 
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what is a pear shaped diamond called