The USGS Saline Aquifer Mapping Project is currently evaluating salinity variations in the Floridan aquifer system utilizing borehole geophysical logs to determine water quality throughout the aquifer system. This study, which contributes to the larger USGS mapping project, gives a detailed mineralogical, petrophysical, and petrographic analysis of core from Cockspur Island using XRD, image analysis software, minipermeametry, and laboratory resistivity measurements. This study investigates how a siliciclastic input in a carbonate aquifer, along with pore geometry, affects the geophysical logs used to calculate salinity. The Lower Floridan aquifer had a significant amount of clinoptilolite, which caused porosity to be underestimated from the sonic log, and illite and smectite, which likely has no effect on the resistivity well log. Cementation factors were found to be significantly larger for grainstones than packstones to wackestones. This study shows that mineralogy and lithology must be taken into account in the USGSs mapping project.