In response to the urgent need to reduce carbon emissions and mitigate the environmental footprint of cement production, low-clinker systems, particularly ternary blends such as Limestone Calcined Clay Cement (LC3), have emerged as promising sustainable alternatives. This study explores the potential of locally sourced raw materials from the western region of Chania, Crete, Greece, to contribute to the development of LC3-type binders. Three clay samples were thermally activated at 700 ℃ and subsequently reacted with saturated lime solutions to evaluate their pozzolanic activity. In parallel, a local marl was calcined at 800 ℃ and hydrated to assess its potential as a reactive filler and binder component in hydraulic mortar formulations. The reactivity of the calcined materials was investigated through their ability to form calcium silicate hydrate (C-S-H) and calcium aluminate hydrate (C-A-H) phases, key contributors to strength development and durability in cementitious systems. Uniaxial compression tests were conducted on hardened cubic samples over a curing period of up to three months to evaluate the evolution of their mechanical performance. Surface roughness analyses were performed on fracture surfaces following three-point bending tests, using microscopic examination techniques to assess surface topography and microstructural features. Results revealed that metakaolin-rich clays displayed significantly higher pozzolanic reactivity with lime, compared to clays with lower kaolinite and higher calcite content. Mechanical testing showed a progressive increase in strength over time, highlighting the importance of extended curing. The performance of these alternative binders proved promising, with strength values comparable to the cement-based control reference.