Rb-Sr dating relies on the beta decay of 87 Rb to Sr with an 87 Rb half-life of 49.61 ± 0.16 billion years. This decay system has been discovered already in 1937, and was later extensively used for isotopic dating of almost any kind of Rb-bearing geologic materials. The attractiveness of the Rb-Sr geochronometer lies in its wide applicability, as both elements occur in most crustal lithologies and are present in µg/g-levels in the majority of rock forming minerals. The contrasting geochemical behavior of Rb and Sr often leads to highly contrasting Rb/Sr ratios between minerals of a given rock, and, in consequence, to large inter-mineral contrasts of Sr isotopic compositions that facilitate precise dating of geologic processes. Rb-Sr mineral data have successfully been used to date crystallization of magmatic rocks as well as high-grade metamorphic processes like eclogitization of subducted crust. Moreover, Rb-Sr dating can also provide age constraints on secondary events such as hydrothermal alteration, hydrothermal vein formation, or deformational events that can cause isotope mobility during fluid-mediated recrystallization or recrystallization as a response to intracrystalline deformation during accommodation of strain in ductile shear zones. Rb-Sr isotopic dating mainly relies on minerals with high Rb/Sr elemental ratios. These minerals are typically K-rich phases, like the phlogopite-annite solid solution series (biotite), different types of potassic white mica, and Kfeldspar. In the classic approach, either whole rock powders or mineral separates are dissolved, followed by wet-chemical separation of Rb and Sr from each other and from the matrix, to avoid the isobaric interference of 87 Rb and 87 Sr during mass spectrometric analysis of Sr isotopic compositions. Only recently laser ablation-ICP-MS-based analytical methodologies have been developed for in-situ dating of Rb-rich mineral phases such as mica or K-feldspar. Unlike the well-established in situ Ar- Ar dating technique, which focuses on the same minerals, in situ Rb-Sr dating offers several distinct advantages. Notably, it eliminates the need for access to irradiation facilities, which can be both time-consuming and costly, and involves handling radioactive materials. In contrast, in situ Rb-Sr dating is significantly less demanding in terms of instrumentation and sample preparation, making it a cost-effective and versatile option that can be implemented in various laboratory settings. Additionally, this method allows for a rapid sample turnaround, enhancing its potential as a widely accessible dating tool suitable for a diverse range of geological targets. The two essential components of suitable laboratory equipment comprise (1) a laser for in situ sampling of the target material and (2) a mass spectrometer capable of (quasi) simultaneously analysing a minimum of three nuclides: 87 Rb, Sr, and 86 Sr or Sr throughout the sample ablation process. Notably, achieving the necessary mass resolution for effectively distinguishing between 87 Rb and 87 Sr (M/∆M ~ 300,000) surpasses the capabilities of any commercially accessible mass spectrometer, so that the use of a collision/reaction cell (CRC) is required. Within the CRC, reactive gases (O 2 , SF 6 , N 2 O, CH 3 F) form Sr-molecule ions such as SrF + or SrO + that can be measured free of the 87 Rbinterference. Interference from mononuclide ions on mass shifted Sr-molecule ions (e.g .