XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1395
Comparison of HIT Axb Tests with Rio Tinto
Geological Classification
The results from the standard HIT Axb tests were compared
with RT’s geological classification and nominal crush-
ing hardness ranking, as shown in Table 3 and Figure 5.
Though the overall trend is consistent, the geological clas-
sification is unable to clearly distinguish the samples in the
intermediate hardness range, which is critical to define the
energy requirements for crushing in industrial operations.
Generation of Small Fragments
The aim of the trial was to determine the applicability of
the HIT for smaller size fractions by comparing the break-
age response of a bed of –2 mm material with the break-
age response of single coarser fragments using the seven
samples supplied for the tests. To this end, the product
from the HIT Axb tests were scalped at 3.35 mm, and the
–3.35 mm material screened to determine the mass distribu-
tion, specifically the +2.0 mm, 2.0×1.7 mm, 1.7×1.4 mm,
1.4×1.18 mm, 1.18×1.0 mm and –1.0 mm. The +3.35 mm
material was further crushed and scalped at 3.35 mm to
reduce the coarser material to essentially 100% –3.35 mm.
The workflow is depicted in Figure 6.
The trials required generation of at least 30g of material
from each of the seven samples, sufficient to undertake at
least three repeat HIT tests using 10g per split. However,
the initial preparation indicated that the HIT products
alone could not provide sufficient mass, as shown in Table 4,
requiring a small proportion of the initial –13.2 mm mate-
rial generated in the initial crushing of the rock lumps to
be subjected to a similar protocol as used on the HIT prod-
ucts. The final mass distributions across the seven samples
were consistent with an average 66:34 split at 1 mm for the
HIT products and 65:35 for the –13.2 mm material.
Table 3. Geological Classification of 7 Samples
RT_Sample_ID Sample Description
Crushing
Hardness
Ranking
Crushing
Hardness
Ranking
Average
Sample HIT -
Axb*
SD of Sample
HIT -Axb*
11202603 Siltstone amorphous gray siltsone hard 6 32 4
11202602 Basalt amorphous, fine-grained basalt medium soft 3 61 12
11202601 Vesiculated basalt Vesiculated basalt soft 2 74 6
11202605 Milky Quartz White milky quartz soft 2 107 3
11202606 Grayish Quartz Grayish, slightly weathered quartz soft 2 96 12
11202607 Granite Compacted, biotite granite/granidiorite very soft 1 130 21
11202604 Weathered Siltsone weathered, slightly friable siltstone very soft 1 331 29
Siltstone
Basalt
Vesiculated basalt
Milky Quartz
Grayish Quartz
Granite
Weathered Siltsone
0
50
100
150
200
250
300
350
400
0 1 2 3 4 5 6 7
Crushing hardness ranking
Figure 5. Relationship between geological hardness classification ranking and HIT Axb test results
HIT
-
Axb
(Average
Sample)
Comparison of HIT Axb Tests with Rio Tinto
Geological Classification
The results from the standard HIT Axb tests were compared
with RT’s geological classification and nominal crush-
ing hardness ranking, as shown in Table 3 and Figure 5.
Though the overall trend is consistent, the geological clas-
sification is unable to clearly distinguish the samples in the
intermediate hardness range, which is critical to define the
energy requirements for crushing in industrial operations.
Generation of Small Fragments
The aim of the trial was to determine the applicability of
the HIT for smaller size fractions by comparing the break-
age response of a bed of –2 mm material with the break-
age response of single coarser fragments using the seven
samples supplied for the tests. To this end, the product
from the HIT Axb tests were scalped at 3.35 mm, and the
–3.35 mm material screened to determine the mass distribu-
tion, specifically the +2.0 mm, 2.0×1.7 mm, 1.7×1.4 mm,
1.4×1.18 mm, 1.18×1.0 mm and –1.0 mm. The +3.35 mm
material was further crushed and scalped at 3.35 mm to
reduce the coarser material to essentially 100% –3.35 mm.
The workflow is depicted in Figure 6.
The trials required generation of at least 30g of material
from each of the seven samples, sufficient to undertake at
least three repeat HIT tests using 10g per split. However,
the initial preparation indicated that the HIT products
alone could not provide sufficient mass, as shown in Table 4,
requiring a small proportion of the initial –13.2 mm mate-
rial generated in the initial crushing of the rock lumps to
be subjected to a similar protocol as used on the HIT prod-
ucts. The final mass distributions across the seven samples
were consistent with an average 66:34 split at 1 mm for the
HIT products and 65:35 for the –13.2 mm material.
Table 3. Geological Classification of 7 Samples
RT_Sample_ID Sample Description
Crushing
Hardness
Ranking
Crushing
Hardness
Ranking
Average
Sample HIT -
Axb*
SD of Sample
HIT -Axb*
11202603 Siltstone amorphous gray siltsone hard 6 32 4
11202602 Basalt amorphous, fine-grained basalt medium soft 3 61 12
11202601 Vesiculated basalt Vesiculated basalt soft 2 74 6
11202605 Milky Quartz White milky quartz soft 2 107 3
11202606 Grayish Quartz Grayish, slightly weathered quartz soft 2 96 12
11202607 Granite Compacted, biotite granite/granidiorite very soft 1 130 21
11202604 Weathered Siltsone weathered, slightly friable siltstone very soft 1 331 29
Siltstone
Basalt
Vesiculated basalt
Milky Quartz
Grayish Quartz
Granite
Weathered Siltsone
0
50
100
150
200
250
300
350
400
0 1 2 3 4 5 6 7
Crushing hardness ranking
Figure 5. Relationship between geological hardness classification ranking and HIT Axb test results
HIT
-
Axb
(Average
Sample)