is the degree to which light is transmitted through
terms used to differentiate the degree of light transmission
through a gemstone are:
Light passes through relatively unobstructed. An image
or object can be seen through the gemstone with
very little distortion (other than due to facets
or double refraction).
Light passes through but is slightly diffused. An image
or object can be seen through the gemstone but with
an indistinct outline or slightly distorted.
Light passes through but objects cannot be distinguished
through the gemstone.
Light passes through only at the thin edges of the gemstone.
No light is transmitted through even at the thin edges
of the gemstone.