These "pocket tranquilizers" use a form of reflexology, or nerve pressure. Rubbing the smooth surface of the stone puts pressure on nerves within the thumb that may release endorphins, the brain's natural relaxants. Worry stones may vary in sizes.
This cleansing stone clears negative energies, and can be used to reprogram other stones. It is a stone of mental clarity, and improves one's connection with the divine. Selenite can be used for scrying into the past, present and future.