<p>The present study presents a characterization framework and testing methodology for characterization of carbonates in a mixed mineralogy soil. A combination of microscale characterization techniques was used to quantify and determine the mineralogical composition of carbonates as well as their distribution within the soil. Thermogravimetric analysis, total carbon content, and acid dissolution tests indicated an average of 24% carbonates uniformly distributed between the coarse and fine fractions of the soil. Elemental composition of the soil sample was obtained using X-ray photoelectron spectroscopy and X-ray fluorescence, and used in conjunction with X-ray diffraction data, which indicated multiple carbonate mineral phases: calcite (major phase), dolomite and ankerite (minor phases), along with quartz, muscovite, and albite as other soil mineral phases. Individual soil particles of these mineral phases were identified using scanning electron microscopy and confirmed with energy dispersive spectroscopy, and furthermore microscopic insights into soil particle shape, texture, and morphology suggested the carbonates were non-porous and likely of abiotic origin. The results indicate that acid dissolution and thermogravimetric analysis provide precise quantification of carbonate content at small sample scales, whereas the loss-on-ignition (LOI) method can provide representative carbonate estimates for larger soil samples. In addition, X-ray diffraction combined with X-ray fluorescence enables reliable identification and differentiation of carbonate mineral phases. The characterization framework and testing protocol developed in this study can be extended to carbonate phases in engineered bio-cementation applications, and more broadly to the identification and quantification of mineral phases relevant to geotechnical engineering applications.</p>