1474 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
25.4 × 19.1 mm Particles
Figure 7 (top left) shows a 5 N/mm2 particle in the 25.4
× 19.1 mm size fraction that does not have large impact
cracks, and Figure 8 (bottom left) shows a 5 N/mm2 parti-
cle in the 25.4 × 19.1 mm size fraction that has large impact
cracks. The 3D images are shown as examples, but most 5
N/mm2 particles in this size fraction have impact cracks. As
expected, many more large impact cracks are present in the
10 N/mm2 particles in the 25.4 × 19.1 mm size fraction,
Figure 6 (right column). As mentioned, these impact cracks
are significant for the sub-surface fluid transportation inside
the coarser particles closer to the diameter of 1 inch. Also,
in the heap leaching, there is compression from the gravity
force, so these impact cracks could be further propagated to
liberate the precious metals for recovery.
After reconstruction of the surface mesh of internal
fractures by Matching Cube, the specific crack surface area
(mm2/mm3) is reported in Figure 8. For 8 mm particles,
the two data points with relatively high specific crack sur-
face areas contain mostly pores and some minor close-to-
surface cracks. A higher HPGR pressure force was required
to propagate impact cracks in 8 mm particles. For the 1.4
cm and 2.2 cm particles, the 5 N/mm2 pressure did create
impact cracks, but a higher HPGR pressure force would
facilitate larger and more impact cracks. The values of
specific crack surface area in the precious metal ore par-
ticles crushed at the pressure of 10 N/mm2 are in the same
magnitude but less compared to the copper ore particles
reported in the previous study (Lin et al., 2012), which is
about 1 to 10 mm2/mm3. It needs to be pointed out that
the previous study used HPGR as a primary grinding, but
the HPGR at Rochester mine is designed for tertiary crush-
ing. Also, the crack propagation in HPGR-processed par-
ticles depends on the ore type, such as hardness.
Figure 7. 3D rendered view of the selected 25.4 × 19.1 mm particles crushed by HPGR at the specific
pressure forces of 5 N/mm2 (left column) and 10 N/mm2 (right column). Color codes for 3D view: green,
contour of particle grey, internal fractures
Figure 8. The specific crack surface area (mm2/mm3) for
selected ore particles
25.4 × 19.1 mm Particles
Figure 7 (top left) shows a 5 N/mm2 particle in the 25.4
× 19.1 mm size fraction that does not have large impact
cracks, and Figure 8 (bottom left) shows a 5 N/mm2 parti-
cle in the 25.4 × 19.1 mm size fraction that has large impact
cracks. The 3D images are shown as examples, but most 5
N/mm2 particles in this size fraction have impact cracks. As
expected, many more large impact cracks are present in the
10 N/mm2 particles in the 25.4 × 19.1 mm size fraction,
Figure 6 (right column). As mentioned, these impact cracks
are significant for the sub-surface fluid transportation inside
the coarser particles closer to the diameter of 1 inch. Also,
in the heap leaching, there is compression from the gravity
force, so these impact cracks could be further propagated to
liberate the precious metals for recovery.
After reconstruction of the surface mesh of internal
fractures by Matching Cube, the specific crack surface area
(mm2/mm3) is reported in Figure 8. For 8 mm particles,
the two data points with relatively high specific crack sur-
face areas contain mostly pores and some minor close-to-
surface cracks. A higher HPGR pressure force was required
to propagate impact cracks in 8 mm particles. For the 1.4
cm and 2.2 cm particles, the 5 N/mm2 pressure did create
impact cracks, but a higher HPGR pressure force would
facilitate larger and more impact cracks. The values of
specific crack surface area in the precious metal ore par-
ticles crushed at the pressure of 10 N/mm2 are in the same
magnitude but less compared to the copper ore particles
reported in the previous study (Lin et al., 2012), which is
about 1 to 10 mm2/mm3. It needs to be pointed out that
the previous study used HPGR as a primary grinding, but
the HPGR at Rochester mine is designed for tertiary crush-
ing. Also, the crack propagation in HPGR-processed par-
ticles depends on the ore type, such as hardness.
Figure 7. 3D rendered view of the selected 25.4 × 19.1 mm particles crushed by HPGR at the specific
pressure forces of 5 N/mm2 (left column) and 10 N/mm2 (right column). Color codes for 3D view: green,
contour of particle grey, internal fractures
Figure 8. The specific crack surface area (mm2/mm3) for
selected ore particles