The file “Compiled Lit Chemistry.csv” dataset compiles the elemental composition of manganese and iron-rich rocks in the terrestrial literature (references included below), NASA Curiosity ChemCam Gale crater, Mars observation point data, and analyses for this paper. The terrestrial literature includes lacustrine, marine, ironstone, ooids, laterite, carbonate, soil, and banded iron formations and compiles major, minor, and trace element data from 1,182 samples. Other columns include a calculation of Fe/Mn ratio, the literature reference number, the type of formation, the location, the speciation of Fe and Mn (carbonate or oxide), the age of the specimen if known, the analytical methods used in the paper, and any special notes about the data or rocks from each paper. Gale crater data comes from the NASA Curiosity rover ChemCam instrument. The geochemical data includes major oxide data and trace element data compiled from the Planetary Data System (PDS) Geoscience Node (https://pds-geosciences.wustl.edu/missions/msl/chemcam.htm). The Mars data only includes Mars sedimentary rocks, removes data from beyond 4.5 m, and only includes MnO ≥ 0.13 wt% (4,751 observation points). This value represents observation points in the upper 25% quartile range for MnO in the Mars ChemCam dataset. This data is used for figures in the manuscript where data from this study are compared to the literature and/or Gale crater. The file “ccam_comps_w-MnO_20210114-Mn sediments.csv” compiles all of the ChemCam Mars major oxide observation point data from the start of the mission to sol 3007. This data only includes observation point data on sedimentary rocks, excluding targets beyond 4.5 m (21,029 observation points). A portion of the data for sols 1000-3007 with RMSEP accuracy error bars is shown in Figure 1 of the manuscript. Trace element data is included for the targets after sol 1000 when available from the PDS. This dataset includes the major oxide precision and Root Mean Squared Error of the Prediction (RMSEP) accuracy uncertainty data, file name, solar day (sol) when the data was collected on Mars, target name, distance, and trace element data with Root Mean Squared Error (RMSE) uncertainty, and notes on the trace element data. For trace element data “