Selenite normally comes in long thin pieces - think ready made wands (!) and is in fact excellent for this purpose as many witches will tell you it controls energy very well. In my own opinion Selenite is every bit as versatile as the universally employed Quartz and it is the one crystal I am never without.
Selenite is also a relatively cheap crystal - the piece pictured here only cost me 80p in a New Age shop.
Selenite is best known among for its properties promoting calm, peace and a sense of wellbeing. In sphere form it has a visual connection with the moon and some witches (Wiccans) employ it as a tool in the drawing down the moon ceremony.
Selenite has a powerful association with healing, particularly healing of the mind. Its an ideal crystal to be carried by those suffering from anxiety or stress.