[en] A novel method for simple, rapid and effective separation of thorium for it’s determination in geological samples such as rocks, and minerals has been developed. Thorium forms 1:2 neutral complex with the bi-dentate ligand, 2,3-dihydroxynaphthalene (2,3-H_2ND), which is extracted into ethylacetate at pH 5-6. Thorium from the organic phase is quantitatively stripped off using dilute hydrochloric acid, and then determined spectrophotometrically as well as by ICP-AES. The effects of variables affecting the quantitative extraction of thorium have been studied in detail. The method has been validated by analyzing certified reference materials (CRM). RSD of the method varied over the range 1 to 5 %. The method has been successfully applied to rocks and minerals. (author)