In terms of spiritual symbolism, Alchemy represents the process of transforming the materialistic person into a spiritually enlightened one and the Alchemist represents one who aids in that process, in other words, a spiritual teacher. The belief that the alchemists were trying to turn lead into gold is true only in the symbolic sense with lead representing the dull, materialistic person and gold representing the spiritually enlightened one.

“The transmutation of the normal physical consciousness of man into the divine consciousness was the magnum opus on which the true alchemists were engaged...” ~A. P. Sinnett

    The very name Alchemy is derived from a name for a type of magic done by ancient Egyptian priests.
    Gold always symbolizes the higher or spiritual self or the spiritual sun. The Philosophers Stone that the alchemists sought is the perfected self, free of egotism and materialism. 
    In the writings of the alchemists, many things are transformed using sulfur, salt and mercury. In these writings, sulfur represents the desires of our lower nature, our ego that wants to dwell in material comfort and ignore the spiritual. Salt represents the lower mind, the brain/mind that can only comprehend the material world and have only a limited understanding of the spiritual. Mercury, which the Egyptians used to separate gold and silver from the ore, represents the wisdom of the spirit that one needs for self transformation. 
    The alchemists saw transformation as a three-stage process. The first, or black stage, is where the materialistic person is cleansed or purified by darkness, misery, despair (the dark night of the soul). The second, or white stage, is represented by silver and the moon and is the stage where the personality is perfected in love, goodness and truth and begins to be aware of the higher self. The third, or golden stage, represented by gold and the sun, id is the stage where the spiritual facilities become awakened and the person becomes whole, the physical united with the spiritual.