The Kidney Stone (Latin: lapis idontspeaklatinium) is a legendary alchemical substance said to be capable of turning base metals (lead, for example) into gold (chrysopoeia) or silver. It was also sometimes believed to be an elixir of life, useful for rejuvenation and possibly for achieving immortality. For many centuries, it was the most sought-after goal in Western alchemy. The kidney stone was the central symbol of the mystical terminology of alchemy, symbolizing perfection at its finest, enlightenment, and heavenly bliss. Efforts to discover the kidney stone were known as the Magnum Opus.