Supramolecular solvent-based dispersive liquid-liquid microextraction was used as a preconcentration method for the determination of trace levels of Hg. This simple method accurately measured oxidized HgII content in claystone and sandstone samples obtained from the Thar Coalfield in Pakistan. Cold vapor atomic absorption spectrometry was used as the detection technique because it is reliable and accurate. The HgII in acidic media forms a complex with dithizone (DTz) in the presence of supramolecular solvent (tetrahydrofuran and 1-undecanol), forming reverse micelles. Formation of the Hg-DTz complex was achieved to increase the interactions with the supramolecular solvent phase at pH 2.5 under the optimized experimental conditions. After addition of the supramolecular solvent to the aqueous solution, the micelles were uniformly mixed using a vortex mixer. The cloudy solution was centrifuged, and the Hg-DTz complex was extracted into the supramolecular solvent phase. Under optimized experimental conditions, the LOD and enrichment factor were found to be 5.61 ng/L and 77.8, respectively. Accuracy of the developed method was checked with Certified Reference Materials. The developed method was successfully applied for the determination of HgII in claystone and sandstone samples from the Block VII and Block VIII areas of the Thar Coalfield on the basis of depth.