In this work, several natural products (three volcanic tuffs, six clays, one diatomite, one bentonite) based on silica have been investigated by instrumental techniques like thermal analysis (TG, DTG, DTA), attenuated total reflectance Fourier transform infrared (ATR-FTIR) and X-ray fluorescence (XRF) spectroscopy, respectively, and specific surface area measurements. These products are fundamentally built of tetrahedral silicate sheets and octahedral hydroxide sheets. Our results show similarities and differences between the analyzed samples related to their origin and nature. The thermal analysis gives information about the mass loss of water coming from adsorption or silanols (%) according to the identity of the natural product. TG (thermogravimetry) curves show the continuous mass loss, DTG (derivative thermogravimetry) the rate of mass loss while DTA's (differential thermal analysis) the nature of thermal effects occur. The thermal analysis proves the loss of adsorption water by endothermic effects (40–175ºC) with a minimum around 110ºC and the loss of water from silanol groups by exothermic effects (175–800ºC) with a maximum around 375º. The results obtained by XRF technique indicate the content of metals of the investigated natural products. One can observe that all analyzed samples contain potassium (0.75–4.37%), iron (0.69–3.21%) and zirconium (0.01–0.04%). Other metals found in the most of samples are calcium, titanium and strontium. The original and demineralized samples were analyzed by ATR-FTIR technique. The compared results of these measurements have better outlined the siloxane and silanol groups. The specific surface area of measured samples is found in the range of 5 to 130 m2/g. The results of this work are useful for the application of these natural products as supports in liquid chromatography and gas/liquid filtration.