I remember from a good while back reading how much gold was...

I remember from a good while back reading how much gold was produced by the original mining operation as a bi-product - can't remember the number right now but from recollection it was pretty significant.

Processing of copper ore uses a froth flotation system (probably not the right technical term) with the copper etc rising to the top on bubbles for collection. Gold and silver present is not captured by this process and instead sinks to the bottom of the vessel and forms a slime. Eventually, this is collected for separate processing. One way or another, the value of that gold and silver goes to the bottom line of CCZ and the processors.