The culet is the bottom facet of a gemstone and should run parallel to the table. However, the term is liberally used in the jewellery industry to describe the bottom point or bottom ridge of a faceted gem.
So as to avoid breakages, sometimes the point is removed at the bottom of the gem and a culet facet is added. This is the reason why some Round Brilliant Cut Diamonds have 57 facets and some have 58. The difference relates to whether the culet has been flattened or not - or The culet can either be a point at the bottom more often whether or not the salesman has a of a gemstone or a flat facet. clue about what he is talking about!
On an octagon cut or emerald cut gemstone, the very bottom of the gem is not a point, but resembles the keel on a boat. All of these are commonly referred to as the culet of the gem.
