The Philosophers' Stone occupied the central place in the entire theoretical structure of transmutational alchemy: it was the hoped for final product of the Great Work, the long, carefully staged sequence of operations, calcination, dissolution, separation, conjunction, fermentation, distillation and coagulation among the most commonly cited, that a base substance was believed to pass through on its way to a state of perfect chemical maturity. Possessing the stone, alchemical texts claimed, would allow its owner to transmute base metals such as lead or tin into gold by projection, casting a small quantity of the stone onto molten base metal, and many traditions additionally credited it with medicinal powers, an elixir of life capable of curing disease and extending the possessor's lifespan far beyond the ordinary.
Descriptions of the stone's physical appearance varied enormously and were not consistent even within a single tradition: some texts describe a red powder, others a heavy crystalline stone, others a strange colored glass or a liquid, and the variation itself is telling, since no consistent, reproducible physical description survives that later chemists have ever been able to match to a real substance obtained by following any surviving recipe. Numerous historical figures claimed success in producing the stone or in witnessing a genuine transmutation performed by another, claims that modern historians of science treat with considerable skepticism, generally attributing reported successes to fraud, contamination of the test metal with trace gold already present, or honest self-deception rather than to any genuine transmutation having occurred.