XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3925
Figure 5, adapted from Little et al., (2016). The illustra-
tion exhibits different grinding actions and associated out-
comes. The progeny from breakage events exhibit breakage
patterns that can be used to identify which comminution
mechanism was dominant in the circuit. Some noteworthy
secondary factors which may further affect the outcome
include, contact energy, for example, whether there were
repeated low energy contacts versus a single high energy
contact, and ore characteristics (e.g., the strength of inde-
pendent components, grain boundaries, and potentially
also the morphology of individual minerals).Thus, when
analysing breakage from liberated diamonds, the mecha-
nisms must be inferred from the surface appearance of dif-
ferent morphologies as observed under the microscope and
using secondary electron and X-ray computed tomography
techniques.
In this study, we define mechanical diamond break-
age as the damage sustained during the extraction of dia-
monds from ore, specifically during initial mining and
subsequent processing. Given the absence of High-Pressure
Grinding Roll (HPGR) and other comminution technolo-
gies that apply the compression breakage mechanism in the
diamond industry in the early 1990s, the Roberts Victor
diamonds underwent processing through a conventional
crushing circuit. The focus of comminution circuits in the
industry at that time was use existing technologies designed
for ore breakage to liberate the diamonds. The comminu-
tion technologies were not primarily designed to mitigate
diamond breakage during the process. In the comminution
processes, compressional and impact forces are most signifi-
cant when, (1) shock waves propagate through rock during
blasting, (2) the ore is treated in scrubber units to remove
fines and reduce large rocks to a size that can be handled
in secondary crushers and during the different crushing
stages applied to liberate the stones, (3) the material drops
from convey belts to storage bins at transfer points, and
(4) the liberated diamonds are transported to holding areas
through pipes using pneumatic conveying systems. Visible
surface indicators and breakage patterns have been identi-
fied on individual diamonds, which are distinct from geo-
logical processes, and can be linked to these ‘high-risk’ unit
operations, correlating with instances of macro-diamond
breakage.
The least severe forms of mechanical fracturing are the
presence of rounded percussion marks, irregular wedge-
shaped attrition marks and abrasion features resembling
‘tram-line’ pits on the outside surfaces of the diamonds.
The percussion and attrition marks are most noticeable on
the smooth surfaces of the secondary dodecahedral dia-
mond morphologies (see Figure 6a), whereas the ‘tram-line’
Figure 5. Illustration of breakage mechanisms encountered in comminution (adapted
from Little et al., (2016)
Figure 5, adapted from Little et al., (2016). The illustra-
tion exhibits different grinding actions and associated out-
comes. The progeny from breakage events exhibit breakage
patterns that can be used to identify which comminution
mechanism was dominant in the circuit. Some noteworthy
secondary factors which may further affect the outcome
include, contact energy, for example, whether there were
repeated low energy contacts versus a single high energy
contact, and ore characteristics (e.g., the strength of inde-
pendent components, grain boundaries, and potentially
also the morphology of individual minerals).Thus, when
analysing breakage from liberated diamonds, the mecha-
nisms must be inferred from the surface appearance of dif-
ferent morphologies as observed under the microscope and
using secondary electron and X-ray computed tomography
techniques.
In this study, we define mechanical diamond break-
age as the damage sustained during the extraction of dia-
monds from ore, specifically during initial mining and
subsequent processing. Given the absence of High-Pressure
Grinding Roll (HPGR) and other comminution technolo-
gies that apply the compression breakage mechanism in the
diamond industry in the early 1990s, the Roberts Victor
diamonds underwent processing through a conventional
crushing circuit. The focus of comminution circuits in the
industry at that time was use existing technologies designed
for ore breakage to liberate the diamonds. The comminu-
tion technologies were not primarily designed to mitigate
diamond breakage during the process. In the comminution
processes, compressional and impact forces are most signifi-
cant when, (1) shock waves propagate through rock during
blasting, (2) the ore is treated in scrubber units to remove
fines and reduce large rocks to a size that can be handled
in secondary crushers and during the different crushing
stages applied to liberate the stones, (3) the material drops
from convey belts to storage bins at transfer points, and
(4) the liberated diamonds are transported to holding areas
through pipes using pneumatic conveying systems. Visible
surface indicators and breakage patterns have been identi-
fied on individual diamonds, which are distinct from geo-
logical processes, and can be linked to these ‘high-risk’ unit
operations, correlating with instances of macro-diamond
breakage.
The least severe forms of mechanical fracturing are the
presence of rounded percussion marks, irregular wedge-
shaped attrition marks and abrasion features resembling
‘tram-line’ pits on the outside surfaces of the diamonds.
The percussion and attrition marks are most noticeable on
the smooth surfaces of the secondary dodecahedral dia-
mond morphologies (see Figure 6a), whereas the ‘tram-line’
Figure 5. Illustration of breakage mechanisms encountered in comminution (adapted
from Little et al., (2016)