Why is a one carat sapphire smaller than a one carat diamond?
A carat is a measure of weight, not size. Sapphire and diamond have completely different chemical compositions. Sapphire has a more dense/heavier specific gravity. A one carat diamond is about 6.5mm when cut properly. A one carat sapphire can vary in it’s diameter due to the cutting process. When cutting diamonds cutters are trying to maximize proportions/brilliance and yield. When cutting colored gemstones the cutter evaluates the stone in a different way. The cutter examines the stone to orient the best color forward. A colored gem must be cut for body color and weight retention therefore the depth and diameter will vary depending on where the best color lies in the rough crystal.
