Size
Though a gemstone's weight is usually given in carats, this may not give an accurate idea of its size, because different types of stone have different densities. Therefore, a 1-carat sapphire or ruby will be smaller than a 1-carat emerald, though they have the same weight, because sapphires and rubies (both a form of the mineral corundum) are more dense than emeralds.
Though a gemstone's weight is usually given in carats, this may not give an accurate idea of its size, because different types of stone have different densities. Therefore, a 1-carat sapphire or ruby will be smaller than a 1-carat emerald, though they have the same weight, because sapphires and rubies (both a form of the mineral corundum) are more dense than emeralds.
Gemstones can also be measured in dimensions (diameter, length, and width). It is important to know the dimensions to ensure that the gemstone weight will be visible and well proportioned in the setting.
Gemstone Learning Guide : Treatment