In an ideally-proportioned diamond, all of the light entering the diamond from the top
will bounce within the diamond and be reflected back through the top, giving the stone
maximum brilliance and fire. If the stone is too shallow or too deep,
some light will escape through the bottom part of the diamond, giving the appearance of
shadows when viewed from the top.
It's easy to see that the deep-cut diamond shown above
will have a higher carat weight, but is clearly the less desirable
stone! Many jewelers will not discuss cut proportions
unless the customer specifically asks; a stone rich in
carat weight but poorly proportioned can be deeply "discounted,"
giving the buyer a false impression of a great deal. Certified diamonds
by the GIA or HRD are graded accoring to their symmetry.
