Like smelting gold ore,
the gold does not exist as a result of smelting.
Though it regains the original golden [quality],
it is perfected only after [the process of] smelting.
Once it becomes true gold,
it cannot become ore again.
– The Sutra of Complete Enlightenment
(Smelting represents spiritual cultivation.
Gold ore represents our defiled nature.
Gold represents our Buddha-nature.)