Selenite is my ultimate favorite of all crystals. It is an angel crystal and needs no clearing plus it can clear all your other crystals within minutes! Selenite will bring in positivity and keep negativity away. <3 You can find this crystal polished, in towers like here, polished stones, long slabs. And it's not expensive!!
A to Z list of Crystals and Gemstones and their metaphysical properties - Crystalinks