Clay, a globally abundant material, has the potential to serve as a cement substitute following calcination. Although the reactivity of kaolinitic clays in this process is well-established, further research is needed to fully understand the potential of low-grade clays with lower kaolinite content in cement production. This study investigated the potential of using clays with low kaolinite content (~22%) sourced from the ceramic industry in the production of limestone calcined clay cement (LC3) by calcining at 750 °C. The chemical composition of the clay was determined by X-ray fluorescence (XRF), and its mineralogical analysis was performed using X-ray diffraction (XRD). The mechanical properties of LC3 mortars were assessed at various water-to-binder ratios and different curing ages. Furthermore, the mineralogical composition of LC3 pastes was characterized using XRD analysis, while the microstructural development of LC3 mortars was investigated through scanning electron microscopy.