XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2643
significantly lower calcite grades compared to the feed
material. The CM and FM products contain more than
50% of the feed calcite with higher grades than the feed.
Finally, the CH and FH products presented a significantly
higher calcite grade, with values over 85%. With the cri-
teria of classification applied, the results suggest that SBS
at early stages of the mineral processing might avoid the
excessive processing of low grade material reducing energy
consumption and potential environmental impact while
maintaining 75% (M and H products) of the material for
further processing. Despite exhibiting high calcite grades,
the CH and FH products fail to meet the stringent speci-
fications of high-purity limestone applications. Therefore,
further separation is necessary to achieve the desired level
of purity for these demanding applications. It is crucial to
emphasize that the optimal classification criteria for SBS
implementation will vary depending on the plant specific
resources, market demands, and processing costs. Careful
consideration is key to strike a balance between maximizing
calcite recovery, meeting essential grade requirements, and
ensuring overall economic feasibility.
Froth Flotation
The undersize and feed samples were floated after crushing
and grinding as baseline to compare with the flotation of
SBS products. The calcite grade and recovery obtained in
these flotations are presented in Table 4. A dedicated clean-
ing test was conducted on the concentrate obtained from
the 10-min ground feed sample, with the goal of evaluating
the feasibility of achieving a concentrate with over 90% of
calcite relying on a two-stage flotation circuit. Regrinding
was necessary prior to flotation to achieve the desired cal-
cite grade. The results are presented in Table 4.
The froth flotation experiments were conducted after
equivalent crushing and grinding to the six SBS products.
The effect of grinding for 5 min and 10 min was evaluated.
Figure 4 shows the calcite grade and recovery obtained in
all flotation experiments. As it was expected, the higher the
Figure 3. XRF sensor response for individual rocks for A) fine fraction, F, and B) coarse fraction, C, in ascending order
Table 3. SBS products characterization
Mass
Distribution (%)
Calcite Grade
(%)
Calcite
Distribution (%)
Quartz Grade
(%)
Quartz
Distribution (%)
CL 24.7 46.0 16.0 30.5 42.8
CM 49.7 75.6 53.0 14.9 42.3
CH 25.6 86.1 31.0 10.2 14.9
FL 25.1 52.7 17.8 30.9 38.1
FM 50.2 77.6 52.4 18.7 46.0
FH 24.7 89.5 29.7 13.1 15.9

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XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2643
significantly lower calcite grades compared to the feed
material. The CM and FM products contain more than
50% of the feed calcite with higher grades than the feed.
Finally, the CH and FH products presented a significantly
higher calcite grade, with values over 85%. With the cri-
teria of classification applied, the results suggest that SBS
at early stages of the mineral processing might avoid the
excessive processing of low grade material reducing energy
consumption and potential environmental impact while
maintaining 75% (M and H products) of the material for
further processing. Despite exhibiting high calcite grades,
the CH and FH products fail to meet the stringent speci-
fications of high-purity limestone applications. Therefore,
further separation is necessary to achieve the desired level
of purity for these demanding applications. It is crucial to
emphasize that the optimal classification criteria for SBS
implementation will vary depending on the plant specific
resources, market demands, and processing costs. Careful
consideration is key to strike a balance between maximizing
calcite recovery, meeting essential grade requirements, and
ensuring overall economic feasibility.
Froth Flotation
The undersize and feed samples were floated after crushing
and grinding as baseline to compare with the flotation of
SBS products. The calcite grade and recovery obtained in
these flotations are presented in Table 4. A dedicated clean-
ing test was conducted on the concentrate obtained from
the 10-min ground feed sample, with the goal of evaluating
the feasibility of achieving a concentrate with over 90% of
calcite relying on a two-stage flotation circuit. Regrinding
was necessary prior to flotation to achieve the desired cal-
cite grade. The results are presented in Table 4.
The froth flotation experiments were conducted after
equivalent crushing and grinding to the six SBS products.
The effect of grinding for 5 min and 10 min was evaluated.
Figure 4 shows the calcite grade and recovery obtained in
all flotation experiments. As it was expected, the higher the
Figure 3. XRF sensor response for individual rocks for A) fine fraction, F, and B) coarse fraction, C, in ascending order
Table 3. SBS products characterization
Mass
Distribution (%)
Calcite Grade
(%)
Calcite
Distribution (%)
Quartz Grade
(%)
Quartz
Distribution (%)
CL 24.7 46.0 16.0 30.5 42.8
CM 49.7 75.6 53.0 14.9 42.3
CH 25.6 86.1 31.0 10.2 14.9
FL 25.1 52.7 17.8 30.9 38.1
FM 50.2 77.6 52.4 18.7 46.0
FH 24.7 89.5 29.7 13.1 15.9

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2644 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
calcite grade of the feed material, the higher calcite grade
obtained in the product. The flotation products obtained
from the CH and FH were above 90% calcite for both 5 and
10 min grinding. While the CH and FH fractions achieved
exceptional calcite contents, the flotation products from the
lower-grade CL and FL fractions also performed admirably,
attaining concentrations above 75%. This demonstrates the
robustness of the froth flotation technique across a diverse
range of feedstock. No significant difference was observed
in calcite grade at 5 or 10 min of grinding for all the SBS
products. However, the longer grinding times did result in
better recoveries for the high (CH and FH) and medium
(CM and FM) grade products.
Figure 4 also highlights a challenge in terms of quartz
contamination since quartz recovery increases alongside
calcite feed grade. This suggests that a higher calcite content
translates to increased mass frothing during flotation, inad-
vertently entraining more quartz particles along the way.
Evaluating alternative flotation methods like column flota-
tion might hold the key to reducing quartz contamination
and achieving even cleaner calcite concentrates.
Case of Study: Queguay Formation Limestone
Valorization
Limestone from Queguay Formation presents a calcite
grade suitable for cement production but not for lime or
pulp plants. Despite the significantly lower consumption
of lime and pulp plants compared to cement production
in the local market, their higher market value for limestone
justifies evaluating co-production strategies. This section
explores two strategic approaches (outlined in Figure 5) to
enhance the market value of Queguay Formation limestone.
Table 4. Calcite grade and recovery obtained in the froth flotation of the undersize and
feed samples with 5 and 10 min of grinding. Additionally, the results obtained from a
cleaner stage applied to the feed sample is presented
Sample
Grinding Time
(min)
Calcite Grade in
Concentrate (%)Calcite Recovery (%)
Feed 5 87.3 ± 1.1 48.5 ± 2.0
10 89.0 ± 0.1 50.9 ± 1.6
Feed (Cleaning) 10 93.8 ± 1.2 71.1 ± 3.0
Undersize 5 87.3 ± 2.0 48.9 ± 2.9
10 84.7 ± 1.0 44.1 ± 2.7
Figure 4. Calcite and quartz recovery, and cumulative grade of the froth products obtained during the flotation of the
previously sorted fractions after 5 and 10 min grinding. Rougher and cleaner concentrate grades for the feed sample are shown
as a reference

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2644 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
calcite grade of the feed material, the higher calcite grade
obtained in the product. The flotation products obtained
from the CH and FH were above 90% calcite for both 5 and
10 min grinding. While the CH and FH fractions achieved
exceptional calcite contents, the flotation products from the
lower-grade CL and FL fractions also performed admirably,
attaining concentrations above 75%. This demonstrates the
robustness of the froth flotation technique across a diverse
range of feedstock. No significant difference was observed
in calcite grade at 5 or 10 min of grinding for all the SBS
products. However, the longer grinding times did result in
better recoveries for the high (CH and FH) and medium
(CM and FM) grade products.
Figure 4 also highlights a challenge in terms of quartz
contamination since quartz recovery increases alongside
calcite feed grade. This suggests that a higher calcite content
translates to increased mass frothing during flotation, inad-
vertently entraining more quartz particles along the way.
Evaluating alternative flotation methods like column flota-
tion might hold the key to reducing quartz contamination
and achieving even cleaner calcite concentrates.
Case of Study: Queguay Formation Limestone
Valorization
Limestone from Queguay Formation presents a calcite
grade suitable for cement production but not for lime or
pulp plants. Despite the significantly lower consumption
of lime and pulp plants compared to cement production
in the local market, their higher market value for limestone
justifies evaluating co-production strategies. This section
explores two strategic approaches (outlined in Figure 5) to
enhance the market value of Queguay Formation limestone.
Table 4. Calcite grade and recovery obtained in the froth flotation of the undersize and
feed samples with 5 and 10 min of grinding. Additionally, the results obtained from a
cleaner stage applied to the feed sample is presented
Sample
Grinding Time
(min)
Calcite Grade in
Concentrate (%)Calcite Recovery (%)
Feed 5 87.3 ± 1.1 48.5 ± 2.0
10 89.0 ± 0.1 50.9 ± 1.6
Feed (Cleaning) 10 93.8 ± 1.2 71.1 ± 3.0
Undersize 5 87.3 ± 2.0 48.9 ± 2.9
10 84.7 ± 1.0 44.1 ± 2.7
Figure 4. Calcite and quartz recovery, and cumulative grade of the froth products obtained during the flotation of the
previously sorted fractions after 5 and 10 min grinding. Rougher and cleaner concentrate grades for the feed sample are shown
as a reference

2642 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
RESULTS AND DISCUSSION
Sensor Based Sorting
The calcite and quartz grade of the fractions after screening
are presented in Table 2. There is a slight enrichment of cal-
cite towards the coarser fractions, C and F. Concerning the
mass distribution of the subsamples, only a 23.1% (C+F)
of the sample mass is suitable for SBS. The undersize frac-
tion, which is unsuitable for SBS, represents a 76.9% of
the original sample and its composition is almost identical
to the feed. The Queguay Formation is characterized by a
non-metamorphosed limestone exhibiting low mechanical
strength and a pronounced tendency for friable fragmenta-
tion upon minimal crushing, resulting in the generation of
a significant volume of fine particles. Table 2 also shows the
LOI values, which are one to two percent higher than the
expected values based on the calcite grade. This discrepancy
can be attributed to the presence of magnesium as dolomite
in relative low grade.
Figure 3 depicts the XRF sensor response for individual
rocks within fractions C and F. Utilizing these measured
values, a classification system based on low (L), medium
(M), and high (H) calcite content categories was established
for both fractions, resulting in the generation of six distinct
product streams. The thresholds defined to separate the cat-
egories were selected to obtained three distinct products,
in terms of calcite grade. The reliability of the XRF sensor
to sort Queguay material was tested in a separated work by
the authors (Tomey, Seiler, de Amores, &Sánchez, 2023).
The characteristics of the SBS products are presented
in Table 3. As expected, the CL and FL products presented
Figure 2. Two stages direct froth flotation procedure
Table 2. Mass distribution and calcite and quartz content of the feed sample and the
three subsamples.
Mass
Distribution
(%)
Calcite Grade
(%)
Quartz Grade
(%)LOI (%)
Coarse (C) 15.6 74.8 15.7 34.2
Fine (F) 7.5 75.4 14.6 34.5
Undersize 76.9 70.2 16.1 33.1
Feed (back calculated) 100 71,3 15,9 33.4

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2642 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
RESULTS AND DISCUSSION
Sensor Based Sorting
The calcite and quartz grade of the fractions after screening
are presented in Table 2. There is a slight enrichment of cal-
cite towards the coarser fractions, C and F. Concerning the
mass distribution of the subsamples, only a 23.1% (C+F)
of the sample mass is suitable for SBS. The undersize frac-
tion, which is unsuitable for SBS, represents a 76.9% of
the original sample and its composition is almost identical
to the feed. The Queguay Formation is characterized by a
non-metamorphosed limestone exhibiting low mechanical
strength and a pronounced tendency for friable fragmenta-
tion upon minimal crushing, resulting in the generation of
a significant volume of fine particles. Table 2 also shows the
LOI values, which are one to two percent higher than the
expected values based on the calcite grade. This discrepancy
can be attributed to the presence of magnesium as dolomite
in relative low grade.
Figure 3 depicts the XRF sensor response for individual
rocks within fractions C and F. Utilizing these measured
values, a classification system based on low (L), medium
(M), and high (H) calcite content categories was established
for both fractions, resulting in the generation of six distinct
product streams. The thresholds defined to separate the cat-
egories were selected to obtained three distinct products,
in terms of calcite grade. The reliability of the XRF sensor
to sort Queguay material was tested in a separated work by
the authors (Tomey, Seiler, de Amores, &Sánchez, 2023).
The characteristics of the SBS products are presented
in Table 3. As expected, the CL and FL products presented
Figure 2. Two stages direct froth flotation procedure
Table 2. Mass distribution and calcite and quartz content of the feed sample and the
three subsamples.
Mass
Distribution
(%)
Calcite Grade
(%)
Quartz Grade
(%)LOI (%)
Coarse (C) 15.6 74.8 15.7 34.2
Fine (F) 7.5 75.4 14.6 34.5
Undersize 76.9 70.2 16.1 33.1
Feed (back calculated) 100 71,3 15,9 33.4