Window Effect
The angles between the numerous facets of faceted cut gemstones should be respected. Frequently, this doesn't happen, which might lead to inappropriate angles that reduce the possible color and result in the so-called "window effect."
In the center of the gemstone, where there is an unintentional loss of light, this effect typically manifests itself. Without returning to the observer's eyes, the light from these regions passes through the gemstone. You may notice this effect by putting the gemstone on a background with contrast and some writing. With a rich window appearance, a transparent gemstone will be simple to read through.
Extinction
The bright regions of the gemstone are described by brilliance, while the dark areas are described by extinction. The darkness is brought on by a reduction in the amount of light that can be transmitted as a result of light rays that are mutually canceled and extinguished as a result of adding up their opposing wavelengths.
Due to a flaw in the cut (improper angles between the facets), or because of internal inclusions in the gemstone (such as a crystalline inclusion), the light penetrating the gemstone may deviate off the ideal path and vanish.
Have you noticed the "Window Effect" and "Extinction" from these stones?
A. No window effect but extinction.
B. Window effect and extinction are noticed.