Acidizing methods for subterranean formations formed of predominantly siliceous material as well as acidizing compositions. Some methods include injecting into a predominantly siliceous subterranean formation, an aqueous acidic mixture formed by blending an aqueous liquid, a fluoride source, and an effective amount of an alkane sulfonic acid, preferably methane sulfonic acid, to adjust the pH of the fluid where the alkane sulfonic acid where the alkane group may be an unbranched, a branched or a cyclic alkyl residue. Hydrofluoric acid (HF) may not be added to the fluid in some embodiments as the fluoride source, such as the case for an HF free fluid, and, in some instances, hydrochloric acid is not added to the fluid to adjust pH. Also described are compositions containing an aqueous acidic mixture formed by blending an aqueous liquid, a fluoride source, and an effective amount of an alkane sulfonic acid to adjust pH.