What is the best stone or gem that represents protection and positive luck?

[Mummy's Booby Fed Bubby]

I am looking for a stone to keep by my bedside that represents protection and good luck. I am wanting to banish or keep away a very negative and hurtful presence, and I am hoping to find a stone which can also bring back happiness and good luck instead of the negativity and bad luck that has been present.
Please only helpful and positive answers!