Search the Bureau of Land Management's website. (References 3) Listed on the website, by region, are reported abandoned land mines. Sites that are being investigated or that have been reported are also listed. The location coordinates are listed for reference.
Examine the maps and records of the county that is said to contain abandoned mines. There are likely land titles recorded with the county recorder's office. Match up the coordinates from the website with maps of the land to create a route.
Call the Bureau of Land Management. Ask to speak to someone about possible abandoned mine locations. Perhaps someone in the office will have information on possible abandoned mines in areas that are not yet released to the public.
Travel to the general location where you think that abandoned mines are located. Make sure to wear safety gear, such as headlamps and helmets. Bring a map along with you as well.