We present the mineralogical, geochemical and geochronological characterisation of the calcite-cemented hydraulic breccia "AUG-B6» and propose it as a reference material for calcite U-Pb geochronology. The material consists of millimeter-sized, well-crystalized sparite crystals that formed rapidly and synchronously [1]. LA-ICP-MS mapping shows relatively high U content together with large variations in the U/Pb ratios. As a consequence, randomly localized laser ablation spot analyses (100 – 150 µm) lead to an ideal dispersion in a Tera-Wasserburg space, with spots reflecting different mixing proportions between radiogenic and common Pb endmembers, and very-well constrained isochrons with MSWD ~ 1. An interlaboratory comparison conducted with various equipment for in-situ analyses (LA-Q-ICP-MS, LA-TQ-ICP-MS, LA-HR-ICP-MS) shows very consistent and reproducible ages, within analytical uncertainties, on various AUG-B6 sub-samples. We show that AUG-B6 can be used as a suitable reference material for in-situ calcite U-Pb geochronology to better estimate the long-term excess-variance and to improve the precision and accuracy of measured ages. Reference [1] Pagel M., Bonifacie M., Schneider D.A., Gautheron C., Brigaud B., Calmels D., Cros A., Saint-Bezar B., Landrein P., Sutcliffe C., Davis D., Chaduteau C., 2018. Chemical Geology 481, 1-17, https://doi.org/10.1016/j.chemgeo.2017.12.026.