One kind of gold mining is digging in the ground for shiny rocks.  Thats not the kind of gold mining this is about.
The other kind of gold mining is finding the "golden person" within ourselfs, The golden man of Eldorado.  The alchemists process to turn lead into gold.  Jason's quest for the Golden Fleece is probably about the same thing.
Discovering our true self.  Our original self.  Our spirit self. This can't be done just by reading books, or joining a church.  It's a process of gradual growth.  The Sun of Righteousness has come to help in that process.