The appearance of highly reflective fault mirrors (FM) (Figure 1) in carbonate rocks is a topic that is only recently receiving interest. Knowing the conditions necessary to produce these FMs is important as it can indicate how the fault ruptured, providing a mitigation tool for appropriate plans to be put in place for similar events in limestone-dominated regions. This is geologically important, has economic significance and could save lives. Recognized FMs occur in carbonate rocks during inferred faulting, which is a common occurrence in the Earth's upper crust (Barnhoon et al 2005), particularly across Mediterranean countries such as Greece and Italy (Smith et al 2011). Fault mirrors have previously been studied at larger outcrop scales, but nanoscale study has been much neglected. Figure 1. Highly reflective FM in EoceneLimestone, Kfar Giladi, Israel (Siman-Tov et al) The first major nanoscale study was undertaken using hand samples of carbonate FM from three different well-preserved localities along the Dead Sea Transform . They were compared to a non-mirror fault surface of the Nahal Uziyahu fault, Gulf of Eilat as a control. The surface topography of the samples was scanned down to the submicron scale using an optical profiler and atomic force microscopy (AFM), both non-contact tools used to map surface profiles using the reflections of a laser beam to accurately map the surface of a sample. The optical profiler is faster but does not have the same resolution as the AFM. Scanning electron microscopy (SEM) was used to visualize surface structures and transmission electron microscopy was used to study a cross-sectional area of ​​the collected samples (Siman-Tov et al 2013). The structures and smoothness of FMs vary depending on the scale (Siman-Tov). An approximately 10–2 m layer of 90–100% matrix called ultracataclasite is observed (Sibson 1977), and the surface exhibits undulations with wavelengths ranging from ~0.1 to 1.0 m in the scale overview. wider outcrop than the surface. Between the hand sample scale and ~1 μm, most observed surfaces showed some subparallel striations but were mostly smooth. Streaks are common on slippery surfaces (Siman-Tov). Roughness decreases as slip increases, suggesting that the area was subjected to large amounts of slip. However, the occurrence of extensional fractures known as Riedel shears branching out from the striations suggests that the area was exposed to a variable amount of slip. When analyzed at the nanoscale, carbonate grains with diameters of tens to hundreds of nanometers are visible (nanograins).