1602 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
CONCLUSIONS
The characteristics of Ag minerals at Gamsberg were inves-
tigated using a systematic study to understand the min-
eralogical properties of the feed, flotation behaviour and
concentrate characteristics. Batch flotation showed that the
majority of Ag was recovered to the low-Mn Pb concentrate
(58.3%) at 87.2 g/t. The Ag recovery followed a similar
sequential recovery trend to that of Pb, as the recovery dif-
ferences between Ag and Pb in the Pb concentrates were
5%. This is mainly due to the recovery of argentite-galena
and native Ag-galena composites, which indicates a rela-
tionship between Ag and Pb. Preferential recovery of Ag
to the Pb concentrate is of little concern since the Ag can
be extracted in downstream processes (e.g., Parkes process).
Close to half of the Ag was recovered to the Zn concen-
trates for the high-Mn ore, whereas only 12% was recovered
for the low-Mn ore. There is a similarity in the high-Mn ore
sequential recovery trends between Ag and Zn, due to the
recovery of more argentite-sphalerite composites compared
to the recovery of native Ag. The sequential recovery trends
between Ag and Zn in the low-Mn ore are dissimilar. This is
due to the recovery of more liberated native Ag as opposed
to argentite-sphalerite composites. The recovery of Ag to
the high-Mn Zn concentrate may in part be due to a func-
tion of the poor galena liberation and galena association
with sphalerite. To enhance Ag recovery to the Pb concen-
trate, improved galena liberation from sphalerite is needed.
Some nano/micro inclusions of Ag-bearing miner-
als within a few galena, sphalerite and silicate grains were
detected, but these, along with the detection of other dis-
crete Ag mineral grains are unlikely to account for the Ag
budget. There is thought to be more Ag hosted elsewhere.
TEM work is recommended for future work to identify
any nano/micro Ag inclusions present in sphalerite, galena
and pyrite. LA-ICP-MS will also determine whether low
concentrations are found in solid solution within these sul-
phides. Silver in pyrite solid solution may be of concern
because it is currently rejected on site. The preferential
recovery of native Ag which was reported to the Zn con-
centrate also requires further investigation. The introduc-
tion of the CuSO4 activator may have accounted for the
improvement in the recovery and grade of Ag in the Zn
concentrate, as the influence of this activator has shown in
improvements in Ag flotation in previous work
D
Native Ag
96.7 wt.% Ag
Pyrrhotite
Galena
Freibergite
14.1 wt.% Ag
Pyrite A
Argentite
90.2 wt.% Ag
B
Sphalerite
Argentite
61.7 wt.% Ag
C
Figure 6. Back-scattered electron (BSE) photos of selected Ag-bearing particles in the high-Mn Pb
concentrate (a), low-Mn Pb concentrate (b), high-Mn Zn concentrate (c), and low-Mn Zn concentrate (d).
Accompanying EDS data for the Ag content in the Ag-bearing mineral is also shown
CONCLUSIONS
The characteristics of Ag minerals at Gamsberg were inves-
tigated using a systematic study to understand the min-
eralogical properties of the feed, flotation behaviour and
concentrate characteristics. Batch flotation showed that the
majority of Ag was recovered to the low-Mn Pb concentrate
(58.3%) at 87.2 g/t. The Ag recovery followed a similar
sequential recovery trend to that of Pb, as the recovery dif-
ferences between Ag and Pb in the Pb concentrates were
5%. This is mainly due to the recovery of argentite-galena
and native Ag-galena composites, which indicates a rela-
tionship between Ag and Pb. Preferential recovery of Ag
to the Pb concentrate is of little concern since the Ag can
be extracted in downstream processes (e.g., Parkes process).
Close to half of the Ag was recovered to the Zn concen-
trates for the high-Mn ore, whereas only 12% was recovered
for the low-Mn ore. There is a similarity in the high-Mn ore
sequential recovery trends between Ag and Zn, due to the
recovery of more argentite-sphalerite composites compared
to the recovery of native Ag. The sequential recovery trends
between Ag and Zn in the low-Mn ore are dissimilar. This is
due to the recovery of more liberated native Ag as opposed
to argentite-sphalerite composites. The recovery of Ag to
the high-Mn Zn concentrate may in part be due to a func-
tion of the poor galena liberation and galena association
with sphalerite. To enhance Ag recovery to the Pb concen-
trate, improved galena liberation from sphalerite is needed.
Some nano/micro inclusions of Ag-bearing miner-
als within a few galena, sphalerite and silicate grains were
detected, but these, along with the detection of other dis-
crete Ag mineral grains are unlikely to account for the Ag
budget. There is thought to be more Ag hosted elsewhere.
TEM work is recommended for future work to identify
any nano/micro Ag inclusions present in sphalerite, galena
and pyrite. LA-ICP-MS will also determine whether low
concentrations are found in solid solution within these sul-
phides. Silver in pyrite solid solution may be of concern
because it is currently rejected on site. The preferential
recovery of native Ag which was reported to the Zn con-
centrate also requires further investigation. The introduc-
tion of the CuSO4 activator may have accounted for the
improvement in the recovery and grade of Ag in the Zn
concentrate, as the influence of this activator has shown in
improvements in Ag flotation in previous work
D
Native Ag
96.7 wt.% Ag
Pyrrhotite
Galena
Freibergite
14.1 wt.% Ag
Pyrite A
Argentite
90.2 wt.% Ag
B
Sphalerite
Argentite
61.7 wt.% Ag
C
Figure 6. Back-scattered electron (BSE) photos of selected Ag-bearing particles in the high-Mn Pb
concentrate (a), low-Mn Pb concentrate (b), high-Mn Zn concentrate (c), and low-Mn Zn concentrate (d).
Accompanying EDS data for the Ag content in the Ag-bearing mineral is also shown