XXXI International Mineral Processing Congress 2024 Proceedings Page 1414 (1438 of 3836)

1467
Latest Advances in 3D Characterization of Ore Particles
for Mineral Processing by High Resolution X-ray
Computed Tomography
Amanda N. Erskine, Jiaqi Jin, Chen-Luh Lin, Jan D. Miller
Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT, USA
Shijie Wang
Coeur Mining, Inc., Chicago, IL, USA
ABSTRACT: A high-resolution 3D imaging method, X-ray Computed Tomography (XCT), has been used
in characterizing ore particles since the 1990s, providing important 3D information on liberation, exposure,
damage, and pore network analysis of packed beds. For the past thirty years, the technologies for high resolution
XCT have kept advancing, including newer X-ray sources, detectors, 3D reconstruction software, and computer
hardware. As a result, significantly higher spatial resolution, larger field of view, better mineral identification, and
more capable image analysis were achieved. This proceeding paper summarizes the recent advances including
porosity in leach columns, micro-cracks in crushed ores, and silver grain exposure in particles studied by the
latest high resolution XCT technology.
Keywords: Micro X-ray computed tomography Heap leach Comminution HPGR Liberation Image pro-
cessing Machine learning.
INTRODUCTION
Compared to the conventional methods to determine per-
meability, X-ray Computed Tomography (XCT) has been
used to characterize the pore network in leach columns in
3D and estimate the permeability based on flow simulation
using the Lattice Boltzmann Method (LBM) (Lin et al.,
2005 Dhawan et al., 2012). Based on the 1 mm resolution
scan, the bottom section of the leach column showed sig-
nificantly less porosity and permeability. With the imple-
mentation of flat panel type detector, the leach column can
be imaged at the voxel size below 100 μm, which would
expose more information of the pore network inside packed
particle bed.
During heap leaching, metals in the exposed grains can
be dissolved by solution at the surface of ore particles. More
importantly, the internal fractures like cracks and pores can
provide a path for solution to diffuse into the subsurface
regions of ore particles, and metals in these subsurface
regions are available for leaching (Liddell, 2005 Ghorbani
et al., 2011). Internal fractures are especially important for
the leaching of coarse particles. Micro-cracks or pores in
coarse particles fundamentally determine the subsurface
solution transportation. In addition to counting particles

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1467
Latest Advances in 3D Characterization of Ore Particles
for Mineral Processing by High Resolution X-ray
Computed Tomography
Amanda N. Erskine, Jiaqi Jin, Chen-Luh Lin, Jan D. Miller
Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT, USA
Shijie Wang
Coeur Mining, Inc., Chicago, IL, USA
ABSTRACT: A high-resolution 3D imaging method, X-ray Computed Tomography (XCT), has been used
in characterizing ore particles since the 1990s, providing important 3D information on liberation, exposure,
damage, and pore network analysis of packed beds. For the past thirty years, the technologies for high resolution
XCT have kept advancing, including newer X-ray sources, detectors, 3D reconstruction software, and computer
hardware. As a result, significantly higher spatial resolution, larger field of view, better mineral identification, and
more capable image analysis were achieved. This proceeding paper summarizes the recent advances including
porosity in leach columns, micro-cracks in crushed ores, and silver grain exposure in particles studied by the
latest high resolution XCT technology.
Keywords: Micro X-ray computed tomography Heap leach Comminution HPGR Liberation Image pro-
cessing Machine learning.
INTRODUCTION
Compared to the conventional methods to determine per-
meability, X-ray Computed Tomography (XCT) has been
used to characterize the pore network in leach columns in
3D and estimate the permeability based on flow simulation
using the Lattice Boltzmann Method (LBM) (Lin et al.,
2005 Dhawan et al., 2012). Based on the 1 mm resolution
scan, the bottom section of the leach column showed sig-
nificantly less porosity and permeability. With the imple-
mentation of flat panel type detector, the leach column can
be imaged at the voxel size below 100 μm, which would
expose more information of the pore network inside packed
particle bed.
During heap leaching, metals in the exposed grains can
be dissolved by solution at the surface of ore particles. More
importantly, the internal fractures like cracks and pores can
provide a path for solution to diffuse into the subsurface
regions of ore particles, and metals in these subsurface
regions are available for leaching (Liddell, 2005 Ghorbani
et al., 2011). Internal fractures are especially important for
the leaching of coarse particles. Micro-cracks or pores in
coarse particles fundamentally determine the subsurface
solution transportation. In addition to counting particles

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1466
Geometallurgy and Process Mineralogy
New Tests and Techniques in Geometallurgy

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1468 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
with cracks (Kodali et al., 2011), using XCT scans with
higher spatial resolution, valuable information regarding
particle damage, such as number of micro-cracks, size, and
surface area of cracks, can be determined. The energy for
particle breakage in HPGR was correlated to the quantita-
tive analysis of particle internal fractures, such as specific
crack surface areas in mm2/mm3 (Lin et al., 2012 Miller
&Lin, 2018).
Deportment of precious metal ores by 2D imag-
ing technologies, such as Scanning Electron Microscope
(SEM), is limited to the number of ore particles mounted
at the polished section surface. The majority of precious
metal resources have a metal grade of around 10 ppm, and
the metal association depends on the ore type. Using a 3D
imaging technique like XCT, the number of ore particles
analyzed can be increased significantly (Wang et al., 2017).
However, the previous generations of micro-XCT, such as
the Xradia-400 system at the University of Utah, are lim-
ited to a practical voxel size of about 2 μm (Miller &Lin,
2018), which is not enough to resolution the micrometer-
size metal grains. With the advance of the latest XCT tech-
nology and computer capability, such-micron resolution
and analysis of large images can easily be achieved.
METHODS
4-inch Leach Column
A Zeiss Xradia 620 system, at the University of Utah nano-
fab, was used to scan the 4-inch leach columns at the voxel
resolution of 68 μm, which was a significantly higher spa-
tial resolution than the milli-scans done in previous study
(Lin et al., 2005). Figure 1 (top) shows the photograph of a
4-inch column inside the XCT instrument, with the X-ray
source on the left and the 3K × 2K flat panel detector on
the sample’s right. A 2D projection image and a section
Figure 1. Top: Photograph of 4-inch column inside the Zeiss Xradia Versa 620 XCT system at the
University of Utah nanofab Bottom-Left: a projected image of the 4-inch column Bottom-Right: a
section of the reconstructed 3D image of the 4-inch column

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Extracted Text (may have errors)

1468 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
with cracks (Kodali et al., 2011), using XCT scans with
higher spatial resolution, valuable information regarding
particle damage, such as number of micro-cracks, size, and
surface area of cracks, can be determined. The energy for
particle breakage in HPGR was correlated to the quantita-
tive analysis of particle internal fractures, such as specific
crack surface areas in mm2/mm3 (Lin et al., 2012 Miller
&Lin, 2018).
Deportment of precious metal ores by 2D imag-
ing technologies, such as Scanning Electron Microscope
(SEM), is limited to the number of ore particles mounted
at the polished section surface. The majority of precious
metal resources have a metal grade of around 10 ppm, and
the metal association depends on the ore type. Using a 3D
imaging technique like XCT, the number of ore particles
analyzed can be increased significantly (Wang et al., 2017).
However, the previous generations of micro-XCT, such as
the Xradia-400 system at the University of Utah, are lim-
ited to a practical voxel size of about 2 μm (Miller &Lin,
2018), which is not enough to resolution the micrometer-
size metal grains. With the advance of the latest XCT tech-
nology and computer capability, such-micron resolution
and analysis of large images can easily be achieved.
METHODS
4-inch Leach Column
A Zeiss Xradia 620 system, at the University of Utah nano-
fab, was used to scan the 4-inch leach columns at the voxel
resolution of 68 μm, which was a significantly higher spa-
tial resolution than the milli-scans done in previous study
(Lin et al., 2005). Figure 1 (top) shows the photograph of a
4-inch column inside the XCT instrument, with the X-ray
source on the left and the 3K × 2K flat panel detector on
the sample’s right. A 2D projection image and a section
Figure 1. Top: Photograph of 4-inch column inside the Zeiss Xradia Versa 620 XCT system at the
University of Utah nanofab Bottom-Left: a projected image of the 4-inch column Bottom-Right: a
section of the reconstructed 3D image of the 4-inch column

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