The quality and value of a sapphire is dependant on a combination of the following criteria:
A sapphire 's weight is measured in carats .5 carats = 1 gram. All other criteria being equal, the greater the carat weight , the rarer the sapphire and the therefore greater its value.
Shape and Cut
To optimize the natural rough ,sapphire are cut into a wide variety of shapes
Cut refers to the accuracy of the angles ,proportions,symmetry and polish of the sapphire .it greatly affects how light travels within the sapphire,and how it exits in the form of brilliance
Colour is a matter of personal preference.sapphire vary in colour depending mainly upon their titanium and iron content, Therefore sapphire from different countries and mines have different predominant colours .Primarily blue, sapphire range from dark and purplish shades to greenish and yellowish ones. But, a natural colour will always have a greater value then a equivalent colour obtained by heating or other processes.
The clarity of a sapphire is determined by the number ,size and location of inclusions which are natural materials present in the stone. They reflect its fascinating geological aspects . Internally and externally too,there may be the presence of fissures, fracture and cavities which affect clarity which affect clarity
Transparency refers to the ability of a sapphire to transmit light . it is affected by the quantity or absence of opacity and brilliance present in the stone.