Uplifting, inspirational and generally lovely to have around as it opens up the crown and higher chakras. It is also a great cleanser.
bear in mind that selenite is water soluble so avoid cleansing with water - instead use sound, incense, intention, though in reality it is fairly self-cleansing.
There are 5 spheres approximately the same size with only slight variations. They are 961-1134g, and have an average diameter of 3.25-3.5cm