This data release reports the mineral abundances in samples of pre-Middle Jurassic basement rocks from twenty-nine (29) boreholes in Florida and southern Alabama. Mineral abundances are quantified from whole-rock powder X-ray diffraction (XRD) data and the Rietveld method and are reported in weight percent or, where present near the detection limit (~1 wt.% depending on mineral), as trace (t). The abundances of expandable clays are given in weight percent in corundum-spiked samples and qualitatively in EG-solvated samples as absent (0), trace (t), present (p), or abundant (a). Accessory minerals identified by optical and/or electron microscopy but not detected in XRD patterns are named but not quantified. Major and trace element geochemical analyses of many of the same samples are available in a companion data release (Deasy and others, 2024a). Raw diffraction intensity data are included in original proprietary formats as well as in converted .csv files. More information about samples and XRD methods and results are included in the accompanying Data Report entitled Petrography and mineralogy of selected pre-Middle Jurassic basement rocks beneath the Atlantic and Gulf Coastal Plains in Florida (Deasy and others, 2024b). Photographs and photomicrographs of all samples are presented in another companion data release (Deasy and others, 2024c). These data were collected to support the characterization, discrimination, and correlation of map units in the Geologic map of pre-Middle Jurassic basement rocks beneath the Atlantic and Gulf Coastal Plains in Florida (Deasy and others, 2024d). This data release contains the following files: DATA_FL-AL_basement_rock_mineral_abundances.csv contains the estimated mineral abundances in eighty-one (81) samples from twenty-nine (29) wells, well identification information and sample depths, trace minerals identified by optical or electron microscopy, results of ethylene glycol (EG) solvation treatments as applicable, angular range of analysis in degrees 2-theta, sample mount types used, modeled mineral compositions as applicable, and optional additional comments. DATA_DICTIONARY_FL-AL_basement_rock_mineral_abundances.csv contains definitions of attributes in the data file. OTHER_ABBREVIATIONS_FL-AL_basement_rock_mineral_abundances.csv lists and defines abbreviations used in this data release. Raw XRD are grouped in a folder (rawXRDdata). Original XRD data, in .xrdml and .raw formats are in three (3) subfolders (rawXRDdata_1, rawXRDdata_2, and rawXRDdata_3) grouped by “data_source” (that is, laboratory in and instrument on which analyses were performed). Diffraction intensity data in .csv format are also included in compiled spreadsheets grouped by “data_source” (rawXRDdata_1.csv, rawXRDdata_2.csv, and rawXRDdata_3.csv). Conversion from original to .csv format was performed with PowDLL Converter v2.7. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.