Abstract: The present invention comprises a method of mining a solid substance, such as coal, minerals, or the like, from an underground deposit in one of a plurality of earth strata. Void areas are created in the deposit so as to generally define an area within the deposit which is to be enclosed. Plugging material is injected into the void areas to form a relatively impervious barrier enclosing the aforementioned area of the deposit and isolating it from the remainder of the earth strata in which it is located. Conversion media, such as solvents or oxidation supporting media, are then injected into the enclosed area to convert the substance therein into flowable form. Finally, the substance as so converted is withdrawn from the enclosed area.