Pendulums are divination tools, used to answer yes/no questions to assist in providing direction.  They work by responding to your subconscious mind.
 
Clear Quartz
Associated with all Chakras
Clear quartz is the most versatile of all stones.  It has amplification properties and can be programmed for any need.  This stone is helpful for all questions & situations.
 
This listing is for 1 pendulum intuitively chosen by me.