XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 39
such as chalcopyrite (CuFeS2) or bornite (Cu5FeS4) that
can be readily recovered through flotation, or the secondary
sulphides and oxides of these minerals that can be recovered
through direct leaching. Below this grade threshold, the
nature of the mineralization changes and instead, Cu sub-
stitutes for other more common elements through isomor-
phous substitution in silicate minerals, such as Cu replacing
Fe in biotite (K(Mg,Fe)3AlSi3O10(OH, F)2) or chlorite
((Mg,Fe)5Al(Si3Al)O10(OH)8). For these two common
silicate rock-forming minerals, Cu does not form part of
the formula describing the mineral. Cu cannot be readily
extracted from these minerals and is known as refractory
material needing more energy-intensive metallurgical pro-
cesses to recover Cu (Manchisi et al., 2019). Such a scenario
is illustrated by Figure 2b indicating the domain of cur-
rent processing of higher-grade ores to the right, the ‘min-
eralogical barrier’ and the domain of refractory material on
the left. This mineralogical barrier represents a techno-eco-
nomic barrier associated with the change over from discrete
minerals hosting valuable metals (e.g., Cu in chalcopyrite)
to Cu replacing other more common elements such as Fe
through atomic substitution in a silicate mineral like biotite
or chlorite. The effect of the changeover
from metals occurring as discrete minerals to those
hosted though isomorphous substitution on the energy per
unit mass of metal recovered is also illustrated in Figure 3,
with the ‘mineralogical barrier’ highlighted to show the
energy threshold that must be overcome to recover the
valuable metal.
Although Skinner (1976) introduced the concept of
the mineralogical barrier relating to the energy barrier that
must be overcome, the concept can be extended to con-
sider the effect of a change in valuable mineralization on
the techno-economic ability to recover that metal and the
need to innovative solutions to overcome the barrier. Some
examples of the innovative solutions would be the imple-
mentation of stirred milling for fine grinding technology
to liberate ultrafine grained sphalerite (Pease et al., 2005)
or platinum group minerals (Schouwstra and Rule, 2016),
or the implementation of cyanidation that saved the gold
industry in South Africa in the 1880s as the easy to pro-
cess oxide gold ore was depleted and the harder to process
unoxidized sulphide ore needed to be treated (Fivaz, 1988).
Understanding the key mineralogical properties of an ore
and its effect on processing is encapsulated by the field of
process mineralogy. Transferring this knowledge gathered
using small-scale or proxy tests to predict ore response and
populating this information into a 3-dimensional block
model to be used for mine planning and optimization is
encapsulated by the field of geometallurgy.
The objective of this paper is to demonstrate the piv-
otal role of process mineralogy and geometallurgy in facili-
tating the sustainable processing of these complex ores,
thus ensuring a successful transition towards cleaner energy
Figure 3. Illustration of the relationship between the energy per unit mass metal recovered versus grade
for geochemically abundant and geochemically scarce metals. Adapted from (Skinner, 1976)
such as chalcopyrite (CuFeS2) or bornite (Cu5FeS4) that
can be readily recovered through flotation, or the secondary
sulphides and oxides of these minerals that can be recovered
through direct leaching. Below this grade threshold, the
nature of the mineralization changes and instead, Cu sub-
stitutes for other more common elements through isomor-
phous substitution in silicate minerals, such as Cu replacing
Fe in biotite (K(Mg,Fe)3AlSi3O10(OH, F)2) or chlorite
((Mg,Fe)5Al(Si3Al)O10(OH)8). For these two common
silicate rock-forming minerals, Cu does not form part of
the formula describing the mineral. Cu cannot be readily
extracted from these minerals and is known as refractory
material needing more energy-intensive metallurgical pro-
cesses to recover Cu (Manchisi et al., 2019). Such a scenario
is illustrated by Figure 2b indicating the domain of cur-
rent processing of higher-grade ores to the right, the ‘min-
eralogical barrier’ and the domain of refractory material on
the left. This mineralogical barrier represents a techno-eco-
nomic barrier associated with the change over from discrete
minerals hosting valuable metals (e.g., Cu in chalcopyrite)
to Cu replacing other more common elements such as Fe
through atomic substitution in a silicate mineral like biotite
or chlorite. The effect of the changeover
from metals occurring as discrete minerals to those
hosted though isomorphous substitution on the energy per
unit mass of metal recovered is also illustrated in Figure 3,
with the ‘mineralogical barrier’ highlighted to show the
energy threshold that must be overcome to recover the
valuable metal.
Although Skinner (1976) introduced the concept of
the mineralogical barrier relating to the energy barrier that
must be overcome, the concept can be extended to con-
sider the effect of a change in valuable mineralization on
the techno-economic ability to recover that metal and the
need to innovative solutions to overcome the barrier. Some
examples of the innovative solutions would be the imple-
mentation of stirred milling for fine grinding technology
to liberate ultrafine grained sphalerite (Pease et al., 2005)
or platinum group minerals (Schouwstra and Rule, 2016),
or the implementation of cyanidation that saved the gold
industry in South Africa in the 1880s as the easy to pro-
cess oxide gold ore was depleted and the harder to process
unoxidized sulphide ore needed to be treated (Fivaz, 1988).
Understanding the key mineralogical properties of an ore
and its effect on processing is encapsulated by the field of
process mineralogy. Transferring this knowledge gathered
using small-scale or proxy tests to predict ore response and
populating this information into a 3-dimensional block
model to be used for mine planning and optimization is
encapsulated by the field of geometallurgy.
The objective of this paper is to demonstrate the piv-
otal role of process mineralogy and geometallurgy in facili-
tating the sustainable processing of these complex ores,
thus ensuring a successful transition towards cleaner energy
Figure 3. Illustration of the relationship between the energy per unit mass metal recovered versus grade
for geochemically abundant and geochemically scarce metals. Adapted from (Skinner, 1976)