In-situ stable Mg isotope analysis of olivine, the most common mineral in igneous and metamorphic rocks, provides critical insights into their formation and timescales. However, accurate correction of significant matrix effects is hampered by the lack of olivine reference materials with forsterite (Fo) content below 80. More importantly, current techniques using secondary ion mass spectrometry (SIMS) or laser ablation-multi collector-ICP-MS (LA-MC-ICP-MS) are insufficient to decipher geological processes occurring at fine scales (<
10 μm). Here, we report potential olivine reference materials with Fo contents ranging from nearly 0 to 90.8, covering a wide range and displaying homogeneous compositions within individual samples. These reference materials were developed through high-temperature experiments and the collection of extraterrestrial meteorites. Using these materials, we established a method for Mg isotope analysis on a CAMECA NanoSIMS 50L, for the first time achieving a high spatial resolution of ∼1 μm with a precision of 0.7-0.8 ‰ (1SD). We found that the matrix effect is best modelled by a BiHill equation with the