The shape of the gem, including finishing touches like facet relationships and polish determine the final beauty of the gemstone. There are a variety of shapes available today with each cut having a critical angle that maximizes light reflection. A badly cut stone would leak light from the bottom and dark stones usually absorb light more than reflect, no matter the cut. The same goes for a deep stone so don’t end up paying for extra carats which don’t add to the gemstone’s beauty. If a shape is rare, you may have to pay a very high price for it so it’s best to know all the common shapes available such as Oval, Cushion, Round, Pear, Octagon ,Heart etc.
The 4Cs are an essential guide but don’t forget that sometimes beauty is found in imperfections. If a gem really pleases you despite its tiny blemish or uneven cut, you might as well buy it. Gemstones, like people, are unique and every stone is beautiful in its own respect.