Part of this symbol is actually a combination of three other symbols representing key substances used in alchemical practices. At the bottom, we see a triangle, which represents sulphur, the circle is a symbol for salt, and the circle toped with a crescent represents mercury. The smaller circle at the top resting inside a larger half circle is the alchemical symbol for 'year'.

The philosopher's stone represents the key that unlocks the final goal of the of the alchemical process. Through its use, the practitioner could transform base metal into something far more valuable (i.e. gold). The stone is also symbolic of quintessence, or the fifth element.