The study of soils is very important in the geological and geological engineering researches. A study of ten samples of soils
was carried out by thermal analysis, and X-Ray Fluorescence Spectrometry to understand soil evolution in Angra dos Reis region,
Rio de Janeiro State, Brazil. The sample collection sites were chosen based on geological characteristics, the soil layer
thickness, the soil composition pattern, and whether or not it was moved either by erosion or by gravitational shifts. Because
of the humid tropical climatic condition, natural soils tend to show great thickness of weathered mantles with formation of
saprolites and saprolite soils. Kaolinite is an important secondary mineral which can be formed from many different minerals,
like k-mica and k-feldspar and can be weathered to gibbsite. The results from TG/DTG and DTA indicated which soils had more weathering, and
the same results were obtained by XRF, when silica/aluminum ratios from samples are compared with thermal analysis results.