Degasification is classified as pre-drainage or post-drainage, depending on whether it is done before or after this process. This process is the primary application of a failure criterion relating major and minor principal stresses called the Hoek-Brown criterion. A form of breast stoping called the room and pillar method is commonly used in this process. Oxidation of sulfides by Acidithiobacillus bacteria can cause an (*) "acid drainage" named for locations for this process. Desired materials obtained through this process typically must then undergo froth (10[1])flotation to remove gangue. (-5[1])Mountaintop removal is an approach (10[1])to this process (10[1])in which explosives are used to (10[1])remove overburden, (10[1])thus exposing underlying seams. For 10 points, name this process in which economically valuable ore (10[1])is extracted from underground. (10[1])■END■