NOVELTY - Microcapsule comprises a core and a shell, where the core comprises alkanesulfonic acid compounds (I), the shell comprises a synthetic or natural wax and the density of the microcapsule is greater than 1 g/cm3.    USE - The microcapsule is useful for acidizing a material within a carbonatic rock formation, to form acidic formulation, which is useful for treating a material (a rock formation and/or a carbonate-containing impurity within a rock formation) for increasing the permeability of an underground carbonatic mineral oil-bearing rock formation, a natural gas-bearing rock formation and/or a hydrothermal rock formation and for dissolving a carbonatic impurity and/or a carbonate-containing impurity, in the production of mineral oil, natural gas and/or geothermal power (all claimed).    ADVANTAGE - The microcapsule: ensures a controlled, continuous and retarded mordant effect on the fissure and pore spaces of underground carbonatic mineral oil- and/or natural gas-bearing or hot water-bearing rock formations in deep wells for mineral oil, natural gas or hot water production, and is barely corrosive with regard to the metallic borehole equipment; can be pumpable in an optimal manner down to large depths in aqueous media without any requirement for higher pump outputs and/or prolonged residence times in the acidizing string; and reduces energy to be expended in the injection of the cooled formation water, by opening the underground migration paths, thus provides higher efficiency and hence higher productivity.    DETAILED DESCRIPTION - Microcapsule comprises a core and a shell, where the core comprises alkanesulfonic acid compounds of formula (R1-SO3H) (I), the shell comprises a synthetic or natural wax and the density of the microcapsule is greater than 1 g/cm3.    R1 = straight, branched or cyclic 1-6C alkyl.    INDEPENDENT CLAIMS are also included for:    (1) method for acidizing, comprising contacting a material with the microcapsule, where the method is suitable for acidizing a material within a carbonatic rock formation;    (2) an acidic formulation, comprising the microcapsule; and    (3) treating a material, comprising injecting the acidic formulation into a rock formation through at least one well, where the process is suitable for increasing the permeability of an underground carbonatic mineral oil-bearing rock formation, a natural gas-bearing rock formation and/or a hydrothermal rock formation, and for dissolving a carbonatic impurity, a carbonate-containing impurity, or both, in the production of mineral oil, natural gas and/or geothermal power.