Measurement of the degree of liberation of ore minerals and their relative quantities in ground ore is needed by mineralogists and mineral processing engineers to assess the performance of concentration operations. Such measurements are routinely made by employing various analytical techniques on 2-D surfaces. This approach overestimates the proportion of free mineral particles in the sample; therefore, appropriate stereological corrections are required to make the liberation estimates more accurate. In addition, there are uncertainties arising from sectioning and measurement of the mineral quantities. High intensity X-ray beams from a synchrotron make microtomographic imaging of solid particles possible at a resolution and sensitivity to resolve compositional differences between certain particles. Several sets of binary particles made of glass and epoxy and the particles composed of lead borate and glass were imaged at the GeoSoilEnviroCARS bending magnet beamline of the Advanced Photon Source at the Argonne National Laboratory. The data were collected using monochromatic X-rays ranging from 15.5 to 30 keV. The samples were rotated about a vertical axis at 0.25° or 0.5° intervals to collect 360 or 720 high-resolution images. Exposure time at each interval was approximately 8 to 10 seconds. Two-dimensional X-ray images obtained at each interval are used to reconstruct a 3-D image of the sample. Following data processing, approximately 500 horizontal slices were made from the 3-D data set for analysis by an image analyzer. In addition, numerous vertical slices were extracted for analysis. Preliminary evaluation of the data based on a limited number of sections indicated variability of approximately 2 % in the modal analysis measurements. In addition, the study demonstrated that the proportion of fully liberated particles is overestimated. The variation in the measurements will be used to develop correction factors for determining the apparent mineral liberation.
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