Why did people eat crushed emeralds during the plague?

Crushed emeralds was one of many remedies used to treat the bubonic plague.  For those who could afford this expensive remedy, emerald gemstones were ground up into a very fine powder using a mortar and pestle.  The powder would then be ingested by the ill patient.  Sometimes it was mixed with a liquid, and other times it was placed on the tongue and swallowed.  It could also be mixed with food.  Even though the powder was finely ground, it still had the texture of crushed glass.  This emerald powder, like most remedies, did nothing to cure the plague.
Those who became ill with the bubonic plague had few effective treatment options.  Little was known about medicine during the Black Death.  In desperation, many turned to remedies.  Remedies ranged from leeches to draining the buboes to drinking mercury.  Most of these remedies caused more harm to the patient's already weakened body.