Diamonds, Surface : Polished

The value of diamonds is always calculated as price/carat. Market prices depend on the "unit price" of the diamond, and this unit price is specific to each weight, color, clarity etc. So the price of a .25-carat diamond is not a quarter of the price of a 1-carat diamond: a .25-carat diamond has its own unit price, and this will always be proportionally lower than that of a similarly colored 1-carat diamond.