Selenite is crystallized gypsum and is generally used for good luck and protection. It will clean, open and activate from the crown chakra up which makes it an excellent choice for spiritual workings of any kind as it eases connections to higher frequencies or higher realms. They bring clear sight and have been used in past to make windows.
There are Selenite windows in the Basilica of Santa Sabina in Rome.
Selenite absorbs and then releases negativity, anxiety and worries which helps to stabilize and balance the emotional body. Energy blockages being removed from the body, although they are energetic in nature, do effect the physical body in varied positive ways depending upon where the blockage was. It is a good stone of reconciliation and is even useful in resolving issues not just in the past but also in past lives.
It has been known not only to help with reconciliation in regard to past lives but has been used to tap into past lives to learn a skill they had in a past life. Selenite makes it possible to be open to memories from the past life, memories of using a skill or skills, that we can carry over into our current incarnation.
Just like it absorbs and releases negativity to stabilize the emotional body it can do the same in the home. If you participate in such activities as cleansing your home, say for example with sage to drive negativity or “bad spirits” away, after doing such a cleansing you can place selenite in the windowsills and near doorways to prevent that negativity from coming back in.
It is associated with the Moon.