The philosopher's stone, or stone of the philosophers is a legendary alchemical substance capable of turning base metals such as mercury into gold or silver. It is also able to extend one's life and called the elixir of life, useful for rejuvenation and for achieving immortality; for many centuries, it was the most sought-after goal in alchemy. The philosopher's stone was the central symbol of the mystical terminology of alchemy, symbolizing perfection at its finest, enlightenment, and heavenly bliss. Efforts to discover the philosopher's stone were known as the Magnum Opus ("Great Work").