A metaphor for the search for enlightenment. Transmuting base metals into gold represents the individual transcending "base" human nature and become one with the divine. The goal is not really the gold, it is the process. From a poem by John Donne entitled Resurrection, Imperfect:
"He was all gold when He lay down, but rose All tincture, and doth not alone dispose Leaden and iron wills to good" (http://www.luminarium.org/sevenlit/donne/resurrection.htm)
Compare Paracelsus, The Book Concerning The Tincture Of The Philosophers, (http://www.levity.com/alchemy/paracel2.html) "The matter of the Tincture, then, is a very great pearl and a most precious treasure, and the noblest thing next to the manifestation of the Most High and the consideration of men which can exist upon earth"
-- StevenNewton
An interesting point, which, depending on your philosophy, you may find very telling and highly amusing: Chinese alchemists searched for the secret to eternal life. European ones searched for the method to turn lead into gold. -- DanielKnapp
I have read that the lead into gold was allegorical, and was a spiritual transformation. The alchemists cloaked their meaning in allegory so that outsiders would not see their goal - the posers would see that the Stone did not change lead to gold, and discard it, while the Enlightened would hold it dear for the spiritual transformation --PeteHardie
Please note: Atom smashers have done the latter (at great expense). Dandilions and bacteria have done the former. Neither is to any great use, except that you can make a salad in a pinch.
Analogous to a trip made for the journey -- not the destination which is only a gateway to the next journey.