I am writing a space colonization game, and I need some guidance on default values for mine productivity. If you also know an estimate of how much people work on them, that's a bonus. Thanks in advance :)
You can get estimates from the USGS mineral yearbooks. For example, the entry on Australia has a data table with the amounts of mined resources. Or, the entry on copper lists both US production and international production, including numbers of people employed.
Digging through those websites will give you an order of magnitude of what to expect.