Colored gemstones are cut into may varied geometric shapes. Many of these shapes have names that clearly indicate the gem’s shape, such as round, oval, pear, square and heart cuts. However, some of the other cuts have names not so indicative of the finished shape of the gem.
I’ll try to define some of the more common shapes in this blog. These descriptions are what you would see if you were looking straight down at the top of a colored gemstone.
Marquise Cut This is basically a two sided stone – kind of a football shaped gem. The industry standardized proportions call for the finished gem’s length to be 2 times the width – 4mm X 8mm, or 6mm X 12mm and so on.
Emerald Cut Is an octagon shaped gem. Is easiest to describe this shape as a rectangle with the four corners slightly cut off at a 45-degree angle. This benefit of this rectangle with the corners nipped off is that the pointed 90-degree corners on a rectangle are a weak area, and, especially with emeralds, are prone to breaking
Cushion Cut If you were to take an emerald cut (described above), and round off the four corners as well as cut a slight curve shape to the four longer sides, you would have a cushion cut. This shape gets its name from the shape of an overstuffed pillow, or cushion you might find resting on a home sofa. A cushion cut gem that is about the same length and width is commonly referred to as an antique cushion cut.
Trillion Cut This is a three sided gem, with all sided being equal in length. This shape is often used as a pair of matching gems set to each side of a larger center stone. When a trillion is larger in size it is often used as a pendant stone, but this shape is an excellent choice for a designer ring.
Cabochon Cut When any shape of a gem is just domed with a convex top and a flat bottom. The name comes from the Middle French word caboche meaning head. Cab cut stones are usually, but not always opaque gems, while faceting is usually applied to transparent stones.