2344 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
and Raman spectroscopy were used to characterize the
modal mineralogy of the non-sulfide gangue (NSG) and
sulfides as well as the carbonaceous material. These miner-
alogical characterizations are important for understanding
overall metal recovery and process performance as well as
providing context for what is possible from a physical min-
eral processing separation perspective.
Textural data had previously been compiled from mill-
stream feed (2020–2022) for valuable minerals (galena
and sphalerite) and sulfide gangue (pyrite). The average
grain size P80 (percent passing 80%) for galena, sphalerite,
and pyrite was 28 µm, 63 µm, and 67 µm, respectively.
Liberation data assumes that particles with sulfide making
up ≥50% of the peripheral length will float. Results indi-
cate 84–92% of sulfides theoretically should float based on
free surfaces available at the current plant grind size.
Eight samples containing varying quantities of carbon
and metal values were included in the test work program.
Samples were crushed to –2 mm and rotary split for TIMA
analysis. The remaining sample was then stage crushed to
–600 µm, screened to –150 µm, and rotary split for Raman
analysis. Raman splits were run through a heavy liquid den-
sity separation to remove sulfides and dense NSG, analyzed
with manual scanning electron microscopy (SEM) to locate
carbon species, and the carbon was analyzed with Raman
spectroscopy.
Modal mineralogy results by TIMA indicate that the
polymetallic ore used in the test work program is predomi-
nately NSG (86%). Within the NSG, swelling clay ranges
from 0–8% (analyzed by cation exchange capacity) and the
non-carbonate carbon reaches up to 0.5%. The main sulfide
detected was pyrite followed by sphalerite and galena with
near-negligible amounts of arsenopyrite. Pyrite concentra-
tions ranged from 3–13%. Sphalerite and galena concen-
trations ranged from 0.1–2% and 0.03–1%, respectively.
Arsenopyrite concentrations reach up to 0.34%. Copper-
bearing sulfosalts were also observed at concentrations up
to 0.41%. Gold and silver phases are all below 0.01%.
While the detrimental impact of carbonaceous mate-
rial on leach gold recovery has been studied previously, and
is understood to a degree, a number of questions regard-
ing the activity of carbonaceous material, and its impact
on flotation recovery has not been defined broadly. Leach
recovery studies have shown that the more structured (less
amorphous) the carbonaceous material is, the smaller the
likely impact on gold leach recovery (i.e., less “robbing” of
the gold in solution). The more active (amorphous) carbo-
naceous material has been shown to have a more significant
impact on gold leach recovery (La Brooy et al., 2017).
The known detrimental impact of carbonaceous mate-
rial (CM) on overall metal recovery therefore stresses the
importance of understanding CM and its effect on flota-
tion (Figure 2). Raman spectroscopy was used to charac-
terize the physical properties of carbon in samples with
varying amounts of CM and these characteristics were used
to interpret process performance.
The samples were classified as low carbon (0.01–0.03%)
or high carbon (0.33–0.53%) based on the organic carbon
concentration determined by leaching carbonate in hydro-
chloric acid and analyzing the residue on a carbon/sulfur
analyzer (Table 1). Samples were also classified by their
gold-robbing capacity, following calculations described in
Miller et al. 2016 (Table 1). This classification was used
as a proxy indicator for carbon activity and the resulting
potential impact on the circuit, with previous observations
indicating more significant negative impacts on flotation
for carbon anticipated to be more active (or amorphous).
Gold-robbing is not solely a function of CM concentra-
tion (Helm et al. 2009 Table 1), so Raman spectroscopy
was used to characterize the degree of disorder of the car-
bon within a sample, and the development of this process
is described in more detail in Baron et al. 2024. The carbon
was then categorized as either crystalline (ordered) or amor-
phous (disordered).
The spectra for individual carbon grains in each sam-
ple were averaged together and grouped into low carbon
Table 1. Carbon and gold-robbing classification for individual samples
Sample ID CM (%)Carbon Content
Carbon Structure
Results
Gold Robbing
Classification
t 0.03 Low Crystaline Non
2 0.02 Low Crystaline Non
3 0.01 Low Crystaline Non
4 0.03 Low Crystaline Non
5 0.53 High Amorphous Highly
6 0.37 High Amorphous Highly
7 0.46 High Amorphous Highly
8 0.47 High Amorphous Highly
and Raman spectroscopy were used to characterize the
modal mineralogy of the non-sulfide gangue (NSG) and
sulfides as well as the carbonaceous material. These miner-
alogical characterizations are important for understanding
overall metal recovery and process performance as well as
providing context for what is possible from a physical min-
eral processing separation perspective.
Textural data had previously been compiled from mill-
stream feed (2020–2022) for valuable minerals (galena
and sphalerite) and sulfide gangue (pyrite). The average
grain size P80 (percent passing 80%) for galena, sphalerite,
and pyrite was 28 µm, 63 µm, and 67 µm, respectively.
Liberation data assumes that particles with sulfide making
up ≥50% of the peripheral length will float. Results indi-
cate 84–92% of sulfides theoretically should float based on
free surfaces available at the current plant grind size.
Eight samples containing varying quantities of carbon
and metal values were included in the test work program.
Samples were crushed to –2 mm and rotary split for TIMA
analysis. The remaining sample was then stage crushed to
–600 µm, screened to –150 µm, and rotary split for Raman
analysis. Raman splits were run through a heavy liquid den-
sity separation to remove sulfides and dense NSG, analyzed
with manual scanning electron microscopy (SEM) to locate
carbon species, and the carbon was analyzed with Raman
spectroscopy.
Modal mineralogy results by TIMA indicate that the
polymetallic ore used in the test work program is predomi-
nately NSG (86%). Within the NSG, swelling clay ranges
from 0–8% (analyzed by cation exchange capacity) and the
non-carbonate carbon reaches up to 0.5%. The main sulfide
detected was pyrite followed by sphalerite and galena with
near-negligible amounts of arsenopyrite. Pyrite concentra-
tions ranged from 3–13%. Sphalerite and galena concen-
trations ranged from 0.1–2% and 0.03–1%, respectively.
Arsenopyrite concentrations reach up to 0.34%. Copper-
bearing sulfosalts were also observed at concentrations up
to 0.41%. Gold and silver phases are all below 0.01%.
While the detrimental impact of carbonaceous mate-
rial on leach gold recovery has been studied previously, and
is understood to a degree, a number of questions regard-
ing the activity of carbonaceous material, and its impact
on flotation recovery has not been defined broadly. Leach
recovery studies have shown that the more structured (less
amorphous) the carbonaceous material is, the smaller the
likely impact on gold leach recovery (i.e., less “robbing” of
the gold in solution). The more active (amorphous) carbo-
naceous material has been shown to have a more significant
impact on gold leach recovery (La Brooy et al., 2017).
The known detrimental impact of carbonaceous mate-
rial (CM) on overall metal recovery therefore stresses the
importance of understanding CM and its effect on flota-
tion (Figure 2). Raman spectroscopy was used to charac-
terize the physical properties of carbon in samples with
varying amounts of CM and these characteristics were used
to interpret process performance.
The samples were classified as low carbon (0.01–0.03%)
or high carbon (0.33–0.53%) based on the organic carbon
concentration determined by leaching carbonate in hydro-
chloric acid and analyzing the residue on a carbon/sulfur
analyzer (Table 1). Samples were also classified by their
gold-robbing capacity, following calculations described in
Miller et al. 2016 (Table 1). This classification was used
as a proxy indicator for carbon activity and the resulting
potential impact on the circuit, with previous observations
indicating more significant negative impacts on flotation
for carbon anticipated to be more active (or amorphous).
Gold-robbing is not solely a function of CM concentra-
tion (Helm et al. 2009 Table 1), so Raman spectroscopy
was used to characterize the degree of disorder of the car-
bon within a sample, and the development of this process
is described in more detail in Baron et al. 2024. The carbon
was then categorized as either crystalline (ordered) or amor-
phous (disordered).
The spectra for individual carbon grains in each sam-
ple were averaged together and grouped into low carbon
Table 1. Carbon and gold-robbing classification for individual samples
Sample ID CM (%)Carbon Content
Carbon Structure
Results
Gold Robbing
Classification
t 0.03 Low Crystaline Non
2 0.02 Low Crystaline Non
3 0.01 Low Crystaline Non
4 0.03 Low Crystaline Non
5 0.53 High Amorphous Highly
6 0.37 High Amorphous Highly
7 0.46 High Amorphous Highly
8 0.47 High Amorphous Highly
