Your question can only be answered in general terms, but here are some considerations:
Variable costs will include, labor, repairs, gasoline, processing, disposal, water, electricity, legal.
Fixed costs will include land purchase or lease, machinery amortization, building amortization, administration, licenses
Other costs might include land access fees, taxes, mineral rights fees, federal and state taxes, land restoration fees, marketing fees (to sell the gold)
The sum of the costs divided by the yield (ounces of gold) will give the cost per ounce.
My suggestions are by no means all inclusive, but they should give you an idea of what might be involved.
