Jacinth

A peculiarly stimulant and tonic effect exercised by the jacinth was noted by Ben Sina (Avicenna), and to this is attributed its value as an antidote for poisons. Not, however, to the material composition of the stone was this effect to be attributed, for it proceeded from the mass in the same way as did the virtue of the magnet. Hence Ben Sina is opposed to the theory that the natural warmth of the body acted upon the jacinth, when taken internally, producing a transmutation, dissolution and mingling of its substance with the volatile spiritual essence.[[274]]

In Constantinople, at a time when the plague was exceptionally prevalent, the citizens used to wear jacinths, because of the special virtues these stones were supposed to possess as guardians against the plague. That jacinth amulets intended for therapeutic use were occasionally to be found in pharmacies, is attested by Ambrosianus, who states that a jacinth the size of a human nail, and set in silver, was kept in a “pharmacy in Poland.” This stone, if held to a wound, was said to prevent mortification.[[275]]

JADE TONGUE AMULETS FOR THE DEAD. CHINESE
Figs. 1–4, plain types; Fig. 5, carved in shape of realistic cicada (a. upper, b. lower face); Figs. 6–9, conventionalized forms of cicada. From “Jade,” by Berthold Laufer.
By courtesy of the author and Field Museum of National History, Chicago.