4
regrind targeting a P80 of 40 microns, hydroseparation of
the reground rougher concentrate and eight cleaning stages
at 750 Gauss. The results reported a final iron concentrate
grade of 65.6% Fe at 12.6% mass recovery (Aminpro,
2023).
Based on the last results, a final laboratory scale com-
plementary testwork program was conducted mainly to
confirm the use of two separated cleaner magnetic separa-
tion lines (750 Gauss and 500 Gauss) and potential recov-
ery improvements via tailings recirculation.
The testwork consisted of sending all the LIMS cleaner
tailings from the more selective line (500 Gauss), via a
hydroseparator, to the LIMS cleaner line conducted at
higher intensity (750 Gauss). The results indicated that, for
the sample tested, an iron concentrate grade of 65.1% Fe
at 11.9% mass recovery was achieved in the more selective
line (500 Gauss) and an iron concentrate grade of 64.5%
Fe at 17.2% mass recovery was achieved in line cleaner cir-
cuit operated at the higher magnetic intensity (Aminpro,
2024). The increase in mass recovery compared to the pre-
vious program at similar concentrate grades was deemed
a significant benefit to the project and therefore tailings
recirculation options were considered in the following cir-
cuit design phase (Ausenco, 2024). Specifically, two paral-
lel cleaner lines were incorporated, one high intensity and
one low intensity, each consisting of eight magnetic sepa-
ration stages and the ability to send the low intensity line
cleaner tailings to the feed of the high intensity cleaner line
(Ausenco, 2024).
Further circuit design refinement was achieved by test-
ing rougher magnetic separation iron concentrate obtained
from the 2023 pilot plant. This focused testwork helped
establish the preferred regrind technology for full-scale
and informed the hydroseparation design. Final iron con-
centrate was also used for thickening and filtration design
confirmation.
Following confirmation of the circuit design a series of
variability tests were conducted to determine the impact of
feed grade, mineralogy and lithology on final iron concen-
trate grade and mass recovery. A total of 38 variability sam-
ples were selected representing the main mineralized
geological units, including Santo Domingo and Iris Norte
through LOM. Each sample was subjected to a copper
rougher flotation test and the tailings fed to the iron separa-
tion circuit. The iron circuit consisted of the following
parameters: low intensity rougher magnetic separation at
1,150 Gauss, followed by rougher concentrate regrind tar-
geting a P80 of 40 microns, hydroseparation of the reground
rougher concentrate and finally eight stages of low intensity
cleaning magnetic separation at 750 Gauss (sample size
limited test to one cleaner circuit flowsheet only, Aminpro,
2024). Results suggested that the anticipated variability in
Santo Domingo ore is amenable to the preferred circuit
design and able to produce iron concentrate at commercial
product grade (Figure 4). This includes high quality iron
concentrate grade at 67% Fe for a proportion of the sam-
ples and commercial iron concentrate grade samples around
65% Fe. Samples achieving below 62% Fe iron concentrate
grade represent minor areas of the deposit, and which valo-
rization is zero in the production plan calculation.
Complementary Testwork
Complementary testwork separate to the primary Santo
Domingo iron concentrator plant design was developed
by the project to evaluate the final iron concentrate qual-
ity and marketing opportunities. The program, conducted
early 2024, consisted of bench and pilot scale pelletiz-
ing testwork at the Natural Resources Research Institute
located at the University of Minnesota (Figure 5 and 6).
The results indicated that the physical and metallurgical
quality of the pellets are acceptable for downstream blast
furnace feed (Table 1).
OPPORTUNITIES
Hematite contained within the Santo Domingo ore body
has been recently tested demonstrating feasibility for iron
concentration up to commercial levels, representing a sig-
nificant opportunity for the project.
CONCLUSIONS
Iron separation focused metallurgical testwork, including
Davis Tube Tests plus bench and pilot scale low intensity
magnetic separation testwork on relevant composite sam-
ples, have allowed for the Santo Domingo iron concentra-
tion plant design.
Figure 4. Statistics of the final iron concentrate for the Santo
Domingo project variability samples
regrind targeting a P80 of 40 microns, hydroseparation of
the reground rougher concentrate and eight cleaning stages
at 750 Gauss. The results reported a final iron concentrate
grade of 65.6% Fe at 12.6% mass recovery (Aminpro,
2023).
Based on the last results, a final laboratory scale com-
plementary testwork program was conducted mainly to
confirm the use of two separated cleaner magnetic separa-
tion lines (750 Gauss and 500 Gauss) and potential recov-
ery improvements via tailings recirculation.
The testwork consisted of sending all the LIMS cleaner
tailings from the more selective line (500 Gauss), via a
hydroseparator, to the LIMS cleaner line conducted at
higher intensity (750 Gauss). The results indicated that, for
the sample tested, an iron concentrate grade of 65.1% Fe
at 11.9% mass recovery was achieved in the more selective
line (500 Gauss) and an iron concentrate grade of 64.5%
Fe at 17.2% mass recovery was achieved in line cleaner cir-
cuit operated at the higher magnetic intensity (Aminpro,
2024). The increase in mass recovery compared to the pre-
vious program at similar concentrate grades was deemed
a significant benefit to the project and therefore tailings
recirculation options were considered in the following cir-
cuit design phase (Ausenco, 2024). Specifically, two paral-
lel cleaner lines were incorporated, one high intensity and
one low intensity, each consisting of eight magnetic sepa-
ration stages and the ability to send the low intensity line
cleaner tailings to the feed of the high intensity cleaner line
(Ausenco, 2024).
Further circuit design refinement was achieved by test-
ing rougher magnetic separation iron concentrate obtained
from the 2023 pilot plant. This focused testwork helped
establish the preferred regrind technology for full-scale
and informed the hydroseparation design. Final iron con-
centrate was also used for thickening and filtration design
confirmation.
Following confirmation of the circuit design a series of
variability tests were conducted to determine the impact of
feed grade, mineralogy and lithology on final iron concen-
trate grade and mass recovery. A total of 38 variability sam-
ples were selected representing the main mineralized
geological units, including Santo Domingo and Iris Norte
through LOM. Each sample was subjected to a copper
rougher flotation test and the tailings fed to the iron separa-
tion circuit. The iron circuit consisted of the following
parameters: low intensity rougher magnetic separation at
1,150 Gauss, followed by rougher concentrate regrind tar-
geting a P80 of 40 microns, hydroseparation of the reground
rougher concentrate and finally eight stages of low intensity
cleaning magnetic separation at 750 Gauss (sample size
limited test to one cleaner circuit flowsheet only, Aminpro,
2024). Results suggested that the anticipated variability in
Santo Domingo ore is amenable to the preferred circuit
design and able to produce iron concentrate at commercial
product grade (Figure 4). This includes high quality iron
concentrate grade at 67% Fe for a proportion of the sam-
ples and commercial iron concentrate grade samples around
65% Fe. Samples achieving below 62% Fe iron concentrate
grade represent minor areas of the deposit, and which valo-
rization is zero in the production plan calculation.
Complementary Testwork
Complementary testwork separate to the primary Santo
Domingo iron concentrator plant design was developed
by the project to evaluate the final iron concentrate qual-
ity and marketing opportunities. The program, conducted
early 2024, consisted of bench and pilot scale pelletiz-
ing testwork at the Natural Resources Research Institute
located at the University of Minnesota (Figure 5 and 6).
The results indicated that the physical and metallurgical
quality of the pellets are acceptable for downstream blast
furnace feed (Table 1).
OPPORTUNITIES
Hematite contained within the Santo Domingo ore body
has been recently tested demonstrating feasibility for iron
concentration up to commercial levels, representing a sig-
nificant opportunity for the project.
CONCLUSIONS
Iron separation focused metallurgical testwork, including
Davis Tube Tests plus bench and pilot scale low intensity
magnetic separation testwork on relevant composite sam-
ples, have allowed for the Santo Domingo iron concentra-
tion plant design.
Figure 4. Statistics of the final iron concentrate for the Santo
Domingo project variability samples