Colored gemstone clarity descriptions vary widely and, despite some efforts, there are no universally accepted guidelines. At The Gem Trader we have come to a consensus which describes the majority of colored stones we see in the market. Our clarity descriptions are described as follows. As individual stones permit, we may grade on a scale between grades, for example, Eye Clean to Slightly Included. In this example, a stone may have a very minor inclusion that is not seen without some difficulty.
Eye Clean (EC)
The highest grade that we give to stones in our inventory this term means that no inclusions are visible to the unaided eye.
Slightly Included (SI)
One or more inclusions may be present and are visible with some effort. Such inclusions generally have a minor effect on appearance and no effect on the durability of the stone.
Moderately Included (MI)
Inclusions are clearly visible and have some effect on appearance, though very little on the durability of the stone.
Heavily Included (HI)
Significant inclusions are present and have a significant effect on the appearance and durability of the stone. This designation is generally used only on the rarest faceted minerals intended for the collector, stones therefore unsuited for use in jewelry.
This is used mainly for cabachon material and refers to the fact the material is too dark to allow light to pass through it.