Geoelectrical methods for evaluating the characteristics of different gypsum varieties in gypsum quarries

Gypsum is a widely used industrial mineral with many applications, most notably in construction. In the extraction of gypsum as a raw material, compositional homogeneity is the main factor affecting the efficiency of the process. A good understanding of the deposit being exploited is paramount for effective planning of the quarrying activity. Currently, this characterization is achieved through drilling, which only provides limited, 1-dimensional information. Electrical Resistivity Imaging (ERI) was employed to assess compositional variations and spatial distribution of gypsum units at the Gelsa quarry, located in Zaragoza, NE Spain. The study aimed to characterize different gypsum varieties, including alabastrine macronodular and layered gypsum, based on their resistivity signatures. ERI data were supplemented with targeted micro–Vertical Electrical Soundings (microVES) to obtain bulk resistivity values of the gypsum units with higher definition, which were used as reference points for interpreting the 2D resistivity sections. The findings revealed that while the resistivity of macronodular gypsum conformed to expected values, layered gypsum exhibited lower-than-expected resistivity despite a high gypsum content. This discrepancy was attributed to the complex lithofacies and secondary microcrystalline gypsum present in the layered units. The results were applied to optimize quarry extraction practices, enabling more homogeneous raw material production. Additionally, an exploratory ERI survey identified areas suitable for future quarry development and ruled out locations with insufficient gypsum resources. The integration of ERI with traditional methods enables more targeted and efficient resource management in gypsum quarries.