I am not a geologist nor do I know if there would be a silver mining company that could use a one mile tunnel, but it might be worth considering?  Given the industrial need for silver and the long time necessary to develop a mine, couldn’t their technology be used in some silver mines to accelerate the process?                  https://www.zerohedge.com/technology/musks-boring-company-build-free-1-mile-tunnel-tunnel-vision-challenge#google_vignette