Wikipedia
Snake-stones, also known as a viper's stones, black stones, '' schwarze Steine'', '' pierres noire'', piedritas negras or serpent-stones, are animal bones or stones used as folk medicine for snake bite in Africa, South America and Asia.
Dr. Linnea Smith from the Yanamono Medical Clinic in the remote Amazon basin of northeastern Peru wrote
The black stone is a fondly held concept in our area, where snakebites are common and sometimes fatal. ... when one lives far from ambulances, med-flights, hospitals, doctors, and when one is confronted with a potentially lethal problem, anything seems better than nothing. Personally, I’d rather have antivenin. Then again, if nothing else is available, what is one to do? And placebo effect is undoubtedly real. ... In any case, better that a person stricken by a snake have some hope than feel completely without recourse...Experts are concerned that relying on a black stone may prevent snakebite victims from seeking appropriate medical help. No scientific study has shown that black stones per se are effective, but, most guidelines for snakebite first-aid stress the need for keeping the victim calm (because acute stress reaction increases blood flow and endangers the victim, and panic is infectious and can compromise judgment).