Intro to Tarot page 219-:
Clear Quartz: brings clarity
Dark Stones: such as smoky quartz crystal or obsidian can keep you centred if you become dizzy or flighty while doing a tarot reading
Rose Quartz: helps to open your heart for compassion
Amethyst: crystal aids in opening the third eye to develop clear psychic vision. If you use just one stone, amethyst may be the best choice overall.