Effective atomic number and density determination of rocks by X-ray microtomography

• Density and effective atomic number of rocks were determined by micro-CT images.
• This methodology employs micro-CT at only one energy.
• It is shown that known heterogeneous rocks can be used as calibration samples.
• Results obtained via micro-CT imaging of unknown rocks were good.

Microtomography, as a non-destructive technique, has become an important tool in studies of internal properties of materials. Recently, interest using this methodology in characterizing the samples with respect to their compositions, especially rocks, has grown. Two physical properties, density and effective atomic number, are important in determining the composition of rocks. In this work, six samples of materials with densities that varied from 2.42 to 6.84 g/cm3 and effective atomic numbers from 15.0 to 77.3 were studied. The measurements were made using a SkyScan-Bruker 1172 microtomography apparatus operating in voltages at 50, 60, 70, 80, 90 and 100 kV with a resolution of 13.1 μm. Through micro-CT images, an average gray scale was calculated for the samples and correlation studies of this value with the density and the effective atomic number of samples were made. Linear fits were obtained for each energy value. The obtained functions were tested with samples of Amazonite, Gabbro, Sandstone and Sodalite.