XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1601
liberated argentite grain in the low-Mn Pb concentrate,
having an Ag content of 90.2 wt.% Ag. All the Ag grains
within these particles are below 10 µm in size. As observed
by the flotation experiments, the sequential recovery of Ag
follows a similar trend to that of Pb in the low-Mn ore due
to the recovery of argentite-galena and native Ag-galena
composites. Primary Ag recovery to the Pb concentrate is
of little concern since the Ag can be extracted from Pb in
downstream metallurgical processes, e.g., the Parkes process
where Zn forms an insoluble compound with the Ag (Tan
and Vix, 2005).
The sequential recovery trends between Ag and Zn
showed to be similar in the high-Mn ore. This is due to the
recovery of more argentite-sphalerite composites compared
to native Ag, as observed by the BSE images but also indi-
cated in Figure 6. Figure 6c illustrates this argentite-sphal-
erite association in the high-Mn Zn concentrate. There
is no similarity in the sequential recovery trends between
Ag and Zn in low-Mn ores. This is due to the recovery of
more liberated native Ag compared to argentite-sphalerite
composites. Figure 6d illustrates a native Ag grain in the
low-Mn Zn concentrate. The reason for the recovery of
native Ag, particularly to the Zn concentrate, needs further
investigation. The pH range used to float the galena and
sphalerite (8.5 to 10.5) and the use of a xanthate collector
(in this case SNPX) is optimal for the Ag flotation. The
introduction of the CuSO4 activator may have significantly
improved the recovery of the liberated native Ag since it is
known that the introduction of CuSO4 can significantly
improve Ag recovery and grade (Drif et al. 2018).
The Ag mineralogy reported in this work is similar to
the typical Ag mineralogy known to be associated with the
Broken Hill, Deeps and Swartberg ores (Rudnick, 2016).
This includes the presence of common discrete Ag-bearing
minerals such as argentite, freibergite, native Ag and
sternbergite. Our work, however, recognizes the presence
of nano/micro inclusions of Ag-bearing minerals within
galena, sphalerite and silicates. Given that the concentra-
tion of Ag in galena and sphalerite was below the detection
limit for SEM-WDS, but that the QEMSCAN detected
measurable Ag (that is not attributed to any form of X-ray
peak overlaps), indicates very fine pixels of high Ag con-
centrations suggesting nano/micro inclusions. Further
interrogation of these nano/micro Ag-bearing minerals
using QEMSCAN surpasses the resolution capabilities of
traditional SEM methods. To study these particles, trans-
mission electron microscopy (TEM) through bright phase
observations of sphalerite, galena and pyrite particles could
be done to identify and more fully characterise these sub-
microscopic Ag-bearing grains. This is not too dissimilar to
studies investigating gold, where submicroscopic colloidal
(nano) gold particles imaged under high resolution micros-
copy are recognised as the bridge between solid solution Ag
in pyrite/arsenian pyrite and discrete gold grains (Reich et
al. 2005).
High-Mn Pb High-Mn Zn Low-Mn Pb Low-Mn Zn 0
10
20
30
40
50
60
70
80
90
100
Ag in SphaleriteSpha
Ag in Galena
Ag in SilicateSili
Malinowskite
Sternbergite
Argentite
Freibergite
Native SilverSil
Figure 5. Distribution of silver in the East pit batch flotation concentrates for the high-Mn and low-Mn ores. The number of
Ag-bearing particles is 17 in the high-Mn Pb concentrate, 24 in the high-Mn Zn concentrate, 10 in the low-Mn Pb concentrate
and 16 in the low-Mn Zn concentrate
Ag
distribution
(%)
liberated argentite grain in the low-Mn Pb concentrate,
having an Ag content of 90.2 wt.% Ag. All the Ag grains
within these particles are below 10 µm in size. As observed
by the flotation experiments, the sequential recovery of Ag
follows a similar trend to that of Pb in the low-Mn ore due
to the recovery of argentite-galena and native Ag-galena
composites. Primary Ag recovery to the Pb concentrate is
of little concern since the Ag can be extracted from Pb in
downstream metallurgical processes, e.g., the Parkes process
where Zn forms an insoluble compound with the Ag (Tan
and Vix, 2005).
The sequential recovery trends between Ag and Zn
showed to be similar in the high-Mn ore. This is due to the
recovery of more argentite-sphalerite composites compared
to native Ag, as observed by the BSE images but also indi-
cated in Figure 6. Figure 6c illustrates this argentite-sphal-
erite association in the high-Mn Zn concentrate. There
is no similarity in the sequential recovery trends between
Ag and Zn in low-Mn ores. This is due to the recovery of
more liberated native Ag compared to argentite-sphalerite
composites. Figure 6d illustrates a native Ag grain in the
low-Mn Zn concentrate. The reason for the recovery of
native Ag, particularly to the Zn concentrate, needs further
investigation. The pH range used to float the galena and
sphalerite (8.5 to 10.5) and the use of a xanthate collector
(in this case SNPX) is optimal for the Ag flotation. The
introduction of the CuSO4 activator may have significantly
improved the recovery of the liberated native Ag since it is
known that the introduction of CuSO4 can significantly
improve Ag recovery and grade (Drif et al. 2018).
The Ag mineralogy reported in this work is similar to
the typical Ag mineralogy known to be associated with the
Broken Hill, Deeps and Swartberg ores (Rudnick, 2016).
This includes the presence of common discrete Ag-bearing
minerals such as argentite, freibergite, native Ag and
sternbergite. Our work, however, recognizes the presence
of nano/micro inclusions of Ag-bearing minerals within
galena, sphalerite and silicates. Given that the concentra-
tion of Ag in galena and sphalerite was below the detection
limit for SEM-WDS, but that the QEMSCAN detected
measurable Ag (that is not attributed to any form of X-ray
peak overlaps), indicates very fine pixels of high Ag con-
centrations suggesting nano/micro inclusions. Further
interrogation of these nano/micro Ag-bearing minerals
using QEMSCAN surpasses the resolution capabilities of
traditional SEM methods. To study these particles, trans-
mission electron microscopy (TEM) through bright phase
observations of sphalerite, galena and pyrite particles could
be done to identify and more fully characterise these sub-
microscopic Ag-bearing grains. This is not too dissimilar to
studies investigating gold, where submicroscopic colloidal
(nano) gold particles imaged under high resolution micros-
copy are recognised as the bridge between solid solution Ag
in pyrite/arsenian pyrite and discrete gold grains (Reich et
al. 2005).
High-Mn Pb High-Mn Zn Low-Mn Pb Low-Mn Zn 0
10
20
30
40
50
60
70
80
90
100
Ag in SphaleriteSpha
Ag in Galena
Ag in SilicateSili
Malinowskite
Sternbergite
Argentite
Freibergite
Native SilverSil
Figure 5. Distribution of silver in the East pit batch flotation concentrates for the high-Mn and low-Mn ores. The number of
Ag-bearing particles is 17 in the high-Mn Pb concentrate, 24 in the high-Mn Zn concentrate, 10 in the low-Mn Pb concentrate
and 16 in the low-Mn Zn concentrate
Ag
distribution
(%)