Abstract The fact that Olmec monumental sculpture exclusively uses basaltic stone requires explanation. Although many possible stone selection criteria are potentially involved in Olmec culture for the deliberate choice of stone, it is unlikely that all or even many were considered when but one stone type (basalt) was chosen for such objects as colossal heads and monumental sculpture. It is suggested here that the consistent correlation between Olmec monumental sculpture and basalt is explicable, based on the deliberate criterion of stone selection for metaphysical reasons and by physical characterization: this mostly dark, vesicular stone was the most compelling reminder of underworld power expressed in volcanism and volcanic mountains, and was thereby appropriated for power in rulership of the Olmec culture.