You just invented block cave mining https://www.e-education.psu.edu/geog000/node/911 https://www.e-education.psu.edu/geog000/node/911 It's been in use for a l

You just invented block cave mining https://www.e-education.psu.edu/geog000/node/911 https://www.e-education.psu.edu/geog000/node/911 It's been in use for a long time and is great for fragmenting large rocks and boulders. It does still need grind after the main fragmentation is done. SAG Mills use the same concept to grind rock to a finer level. Most of the abrasion is rock-on-rock inside the mill.