In this research article, we have demonstrated how spectrometric properties of diagnostic absorption features of rocks imprinted in their reflectance spectra can be used to delineate economic rocks (limestone, bauxite and gossans) from the adjacent country rocks. Spectral features or absorption features of rocks, discussed in this paper, are identified based on the comparative analysis of spectral feature of diagnostic constituent minerals of these rocks. It has also been observed that the each economic rock can be separated from their respective "background" country rock(s) based on the combination of certain spectrometric properties (wavelength of absorption feature and asymmetry) of their respective diagnostic absorption features imprinted in their reflectance spectra. The study also revealed that the separability of these economic rocks from their respective host rock will be affected if spectral profiles of mixed set up (where economic rocks are linearly mixed with the associated country rocks within the field of view of spectroradiometer) are collected instead of pure rocks. This observation justifies the fact that size of minimum distinguishable unit (i.e., pixel in case of spectral data presented as a image) of spectral measurement should be less than the size of the exposure/target, for effectively separating one pure target i.e., an economic rock from the associated country rocks.

The gossan exposures are sparsely distributed in the Dariba area and for detection and mapping of gossan and its associated lithology, spectral signatures have been used. Spectral reflectance and absorption features in VNIR-SWIR (visible and near-infrared - shortwave infrared) domain provide the scope for delineating the mineralogy of rocks. In the study, a few spectral mapping methods like Spectral angle mapper, Spectral information divergence and Band ratio indices were applied to ASTER (Advanced Space borne Thermal Emission Reflection Radiometer) calibrated data for delineating the lithology. These mapping methods could delineate boundaries for gossan and its associated rocks of Dariba; but above out of all mapping methods, spectral angle mapper spatial map has been validated with base detailed geological map in quantitatively and accuracy much better than spectral information divergence indices. The band ratio can demarcate the boundaries for gossans in the 4/2 ratio map, in the same way for associated rocks of Carbonates were well delineated in the (7+9)/8 ratio map and Quartzite 4/6 ratio map. Finally, the overextended boundaries of Dariba gossans and associated units found in the above validated spatial map, can be confirmed with field evidence can be helpful to update the base map of Dariba