Bakırköy Küfeki Stone: A Heritage Stone Nominee with regards to the UNESCO World Heritage Site of Istanbul, Türkiye

Natural stone not only endures; it records cultural memory. Bakırköy Küfeki Stone, a Miocene biosparitic limestone, historically quarried near present-day Bakırköy where is a district in Istanbul, and as the relevant lithology is most commonly found within the boundaries of this district, the stone has been named accordingly underpinned the architectural fabric of Istanbul’s Historical Peninsula (UNESCO World Heritage Site), spanning the Roman and Ottoman eras (e.g. city walls, aqueducts, major churches and mosques). Rapid urbanization has removed access to the original quarries. As a result, recent restorations have often substituted lithologies that mimic color/texture but differ in provenance and engineering behavior, which may hasten decay and compromise authenticity. This study assesses Bakırköy Küfeki Stone as a Global Heritage Stone Resource (GHSR) nominee by documenting its historical use, quarry distribution, geological context, and by characterizing mineralogical–petrographic, geochemical, and physico-mechanical characteristics (XRPD, WD-XRF, density, water absorption, porosity, uniaxial compressive, tensile, and abrasion strengths, frost resistance). Findings indicate a calcite-dominated, porous stone that is workable when freshly extracted yet hardens with time, a behavior consistent with its long service life but also with observed deteriorations such as erosion, dissolution, black crust (gypsum) formation, granular disintegration, and biological colonization under humid, polluted urban atmospheres. We discuss weathering pathways, restoration outcomes, and risks posed by non-equivalent replacements. To sustain both material integrity and urban identity, the paper proposes identifying and qualifying new sources that match the original stone potentially in Türkiye (e.g. Çanakkale) and in abroad using standardized testing and performance-based acceptance criteria. Formal GHSR recognition would, in turn, support better sourcing, documentation, and conservation planning across Istanbul’s heritage assets.