An analysis from the Government Accountability Office reveals that the government does not keep track of the amount and value of hardrock minerals – gold, silver, copper, etc. – mined on public lands that are being given away to private companies.
Because the government does not collect royalties on these minerals, it claims there is no reason to keep track of this information:
We found that federal agencies generally do not collect data from hardrock mine operators on the amount and value of hardrock minerals extracted from federal lands because there is no federal royalty that would necessitate doing so.
The reason that companies mining hardrock minerals on public lands are exempt from paying royalties is a law passed almost 150 years ago, called the General Mining Act of 1872. To this day, it is the law of the land when it comes to extracting hardrock minerals from the federal estate. This means that mining companies are able to extract taxpayer-owned copper, gold, silver, and other minerals for nearly nothing in exchange.