XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1391
In order to address this void, a new device has been
developed, exploiting a central feature of single particle
impact testing—that the Axb can be reliably estimated
using one precise low energy test, and that the Bond grind-
ability can be linked to the breakage response at one pre-
cise high energy test. This device, called the Hardness Index
Tester (or HIT), has been precision engineered to allow
users to break narrowly sized fragments at a set specific
energy, in a safe and easy manner. On pre-sized fragments, a
single test using 20 fragments takes less than five minutes to
complete, and the results are immediately available. Details
of the HIT development and successful applications can be
found in technical papers by Kojovic (2016), Bergeron et al
(2017), Leetmaa et al (2019) and Varianemil et al (2023).
However, even the HIT device was seen as unsuitable
for exploration stage ore characterization since the stan-
dard HIT test protocols required fragments coarser than
10 mm. This limitation was discussed in industry explo-
ration forums regarding HIT applications for small frag-
ments to infer Axb and BWi hardness.
Rio Tinto Exploration initiated a small proof-of-con-
cept trial supplying 7 rock samples with expected wide
range of hardness. The extension of the standard HIT test
to particles with chosen fraction size less than two milli-
metres followed the work described by Whiten (2020) in
which the JKDWT tester was used to break a bed of par-
ticles. Whiten’s test breaks a bed of about 10 grams of par-
ticles in a narrow size fraction. Typical bed size is about 35
millimetres in diameter and 3 millimetres deep. The bed
is retained by ring made of Scotch strapping tape, which
has longitudinal strength but crosswise requires minimal
energy to collapse.
The question whether bed breakage tests using the HIT
can align with single particle breakage tests was addressed at
the Brisbane Metallurgical Lab who completed the sample
preparation, crushing &screening, standard HIT Axb tests
and new small fragment HIT tests using a bed of narrowly
sized particles.
This paper focuses on the application of the HIT device
in unconfined bed impact breakage tests using fragments
below 2 mm, and correlation of results with Axb measure-
ments on coarser fragments. This work is seen separate to
the significant research conducted on confined particle bed
compression breakage tests (Schönert, 1988 and 1996) and
more recent development of Piston &Die bed breakage
tests at UBC (Davaanyam, 2015). The latter tests are much
slower and require equipment that is not readily available
for rapid application at the exploration phase.
HIT DESCRIPTION
SimSAGe Pty Ltd developed the HIT for rapid rock-
hardness determination at the mine site, allowing on-the-
spot determination of rock hardness variability. The HIT
exploits a central feature of single particle impact testing,
by which the Axb can be reliably estimated using one pre-
cise low-energy test (Kojovic, 2016 Napier-Munn et al.,
1996). Results from several industrial trials confirmed the
HIT was able to align with the Axb derived using the JK
Drop Weight Test or SMC Test, providing the same frag-
ments were used in both test methods, including the initial
fragment selection and product sizing protocol. Figure 1
shows the second generation HIT device, which comprises
a frame, a sample cup to hold the fragment to be crushed,
crusher hammer assembly, and dual lever mechanism
Figure 1. Image of HIT device and close-up of broken rock in cup
In order to address this void, a new device has been
developed, exploiting a central feature of single particle
impact testing—that the Axb can be reliably estimated
using one precise low energy test, and that the Bond grind-
ability can be linked to the breakage response at one pre-
cise high energy test. This device, called the Hardness Index
Tester (or HIT), has been precision engineered to allow
users to break narrowly sized fragments at a set specific
energy, in a safe and easy manner. On pre-sized fragments, a
single test using 20 fragments takes less than five minutes to
complete, and the results are immediately available. Details
of the HIT development and successful applications can be
found in technical papers by Kojovic (2016), Bergeron et al
(2017), Leetmaa et al (2019) and Varianemil et al (2023).
However, even the HIT device was seen as unsuitable
for exploration stage ore characterization since the stan-
dard HIT test protocols required fragments coarser than
10 mm. This limitation was discussed in industry explo-
ration forums regarding HIT applications for small frag-
ments to infer Axb and BWi hardness.
Rio Tinto Exploration initiated a small proof-of-con-
cept trial supplying 7 rock samples with expected wide
range of hardness. The extension of the standard HIT test
to particles with chosen fraction size less than two milli-
metres followed the work described by Whiten (2020) in
which the JKDWT tester was used to break a bed of par-
ticles. Whiten’s test breaks a bed of about 10 grams of par-
ticles in a narrow size fraction. Typical bed size is about 35
millimetres in diameter and 3 millimetres deep. The bed
is retained by ring made of Scotch strapping tape, which
has longitudinal strength but crosswise requires minimal
energy to collapse.
The question whether bed breakage tests using the HIT
can align with single particle breakage tests was addressed at
the Brisbane Metallurgical Lab who completed the sample
preparation, crushing &screening, standard HIT Axb tests
and new small fragment HIT tests using a bed of narrowly
sized particles.
This paper focuses on the application of the HIT device
in unconfined bed impact breakage tests using fragments
below 2 mm, and correlation of results with Axb measure-
ments on coarser fragments. This work is seen separate to
the significant research conducted on confined particle bed
compression breakage tests (Schönert, 1988 and 1996) and
more recent development of Piston &Die bed breakage
tests at UBC (Davaanyam, 2015). The latter tests are much
slower and require equipment that is not readily available
for rapid application at the exploration phase.
HIT DESCRIPTION
SimSAGe Pty Ltd developed the HIT for rapid rock-
hardness determination at the mine site, allowing on-the-
spot determination of rock hardness variability. The HIT
exploits a central feature of single particle impact testing,
by which the Axb can be reliably estimated using one pre-
cise low-energy test (Kojovic, 2016 Napier-Munn et al.,
1996). Results from several industrial trials confirmed the
HIT was able to align with the Axb derived using the JK
Drop Weight Test or SMC Test, providing the same frag-
ments were used in both test methods, including the initial
fragment selection and product sizing protocol. Figure 1
shows the second generation HIT device, which comprises
a frame, a sample cup to hold the fragment to be crushed,
crusher hammer assembly, and dual lever mechanism
Figure 1. Image of HIT device and close-up of broken rock in cup