Basically, the more color in colored stones, the better. Color depth and purity are linked with value and price. Color depth does not mean a darker color, but that the color should be rich. Inky black sapphires are too dark and although promoted as desirable and valuable, they belong at the bottom of the market. With blue sapphires, the specific shade of blue that appeals to individuals is highly personal.
Clarity refers to the absence of internal flaws or inclusions.
Type and placement of flaws are also very important. Sapphires almost always contain inclusions and even quality sapphires are lightly included. If you find a flawless stone, you would be wise to question whether it is synthetic or an imitation. Nature almost never makes sapphires, rubies or emeralds without inclusions. Dark sapphires show fewer inclusions but lack the fire and brilliance of their lighter counterparts.