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.
Howlite is a borate mineral found in evaporate deposits. It was first discovered in Nova Scotia in 1868 by Henry How when miners in a gypsum quarry found it to be a nuisance. It is a whitish-gray colour with gray veins in a web-like pattern. Howlite is often dyed to resemble other stones such as turquoise or chrysocolla.
As a healing stone howlite is calming; used to relieve tension and anxiety. Place a piece of howlite under your pillow to fight insomnia.