The 1,3-benzenediamidoethanethiol ligand (BDET) completely precipitates soft heavy metals from aqueous solutions under a wide range of conditions. In the present study, the sodium salt of this ligand was applied during the cyanide leaching of ore samples collected from an active gold-mining site in South America. The ligand irreversibly binds mercury from solutions containing cyanide, similarly to those present in the gold-cyanide process (GCP). The present work tests the industrial viability of BDET in the GCP through a column leaching study on ores from South America. The average mercury concentration in the ore samples was 5.22 ppm (milligrams of Hg per kilogram of ore), leached by 19.1% after cyanide extraction. After addition of BDET to the extractant solution, leached mercury from the columns decreased to 0.001 ppm, whereas the leached gold and silver concentrations remained unaffected.