I suggest that the physical object that Joseph had in his possession was not literally ancient gold plates, but plates of his own creation which talismanically represented the "gold plates" of his visions, aiding his mystical translation of those visions.
A tradition of a "heavenly book" runs through many traditions, including Mormonism with its "gold plates." What spiritual reality might these traditions be pointing to?
Language often constructs our perception of reality. As the philosopher William H. Gass once said, "The true alchemists do not change lead into gold; they change the world into words." Or so they try.
In my paper "The Book of Mormon as Literary Alchemy: Joseph’s Magnum Opus and the Philosopher’s Stone," I suggested that the "gold plates" that Joseph Smith had in his possession were not actually made of gold, and did not actually contain ancient historical records like Mormons traditionally think. But that doesn't mean that there were not "gold plates" which were a kind of "hidden treasure" that Joseph really did discover within himself, which was the source of real divine wisdom, "ancient wisdom," and which he taught could be found within all people as well.
Joseph Smith's activity in bringing forth the Book of Mormon can be viewed as a project of alchemy, which was influenced by his affiliation with treasure digging, the folk magic worldview, the Hermetic tradition,1 as well as his many mystical spiritual experiences. I suggest he initially sought to bring the “gold plates” of his visions into material reality, and in the process discovered the true “gold” was within himself, the elusive Philosopher’s Stone.