What is Selenite?
Selenite is a gypsum crystal which can be found all over the world. These crystals feature a white, translucent color but you can sometimes find them dyed various colors!

What are the benefits of Selenite?
Selenite is used to cleanse and clear other stones. This powerful rock is believed to carry a high vibration–that of the angelic realms! Selenite also can be left around rooms in a home to cleanse the atmosphere.
When should someone get Selenite?
One should seek selenite if in need of mental clarity, stress relief or during any decision-making. The metaphysical properties of Selenite help stabilize emotions and clear energetic blockages.

Reference:
Selenite by Crystal Life https://www.crystal-life.com/selenite-2/