38 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
amount of Fe in the mineral is captured by the mineral
formula. In theory, if one wanted to recover Fe, a rock
such as a basalt or a gabbro in which the key minerals are
olivine and pyroxene might be a good place to start look-
ing. In practice, however, one would rather search for an
Fe-ore deposit, where geological processes have produced
a concentration of Fe-bearing minerals such as magnetite
(Fe3O4) or hematite (Fe2O3). Regardless, there is no short-
age of rocks that contain Fe-bearing minerals, with many
rocks also containing accessory magnetite or hematite. This
can be graphically illustrated as in Figure 2a which shows
the relationship between the valuable metal grade and
tonnage as a normal distribution. With decreasing metal
grades, the volume of material potentially available for
processing increases although the processing costs would
concomitantly increase due to the larger volume of gangue
minerals that need to be comminuted and rejected. The
larger the volume of gangue minerals that need to be com-
minuted for liberation of the valuable minerals, the greater
the energy used per unit mass of Fe recovered (Figure 3).
For geochemically scarce metals, however, the form
in which they occur has a major relationship to metal
grade. Above a certain grade, the valuable metal occurs as
a major element in a discrete mineral, and it is only due
to a unique set of ore-forming processes that this grade
threshold is obtained. In the case of Cu occurring above
this grade threshold, one would expect to find Cu occur-
ring as a major element in a discrete Cu-bearing mineral
2000 2010 2020 2030 2040 2050
0
10000
20000
30000
40000
Year
Mining
Recycling
Historical Projected
Figure 1. Historical (pre-2019) and projected zinc supply derived from mining and metal recycling. The
projected scenarios are based on a ‘business as usual’ case. The range in projected Zn demand in 2050 is
also shown. Adapted from Rostek et al. (2023)
Figure 2. Illustration of the relationship between metal abundance and grade for (a) a geochemically abundant metal such as
Fe, and (b) a geochemically scarce metal such as the critical metals. Adapted from Skinner (1976)
Zn
production
(kt/a)
Projected
demand
in2050
amount of Fe in the mineral is captured by the mineral
formula. In theory, if one wanted to recover Fe, a rock
such as a basalt or a gabbro in which the key minerals are
olivine and pyroxene might be a good place to start look-
ing. In practice, however, one would rather search for an
Fe-ore deposit, where geological processes have produced
a concentration of Fe-bearing minerals such as magnetite
(Fe3O4) or hematite (Fe2O3). Regardless, there is no short-
age of rocks that contain Fe-bearing minerals, with many
rocks also containing accessory magnetite or hematite. This
can be graphically illustrated as in Figure 2a which shows
the relationship between the valuable metal grade and
tonnage as a normal distribution. With decreasing metal
grades, the volume of material potentially available for
processing increases although the processing costs would
concomitantly increase due to the larger volume of gangue
minerals that need to be comminuted and rejected. The
larger the volume of gangue minerals that need to be com-
minuted for liberation of the valuable minerals, the greater
the energy used per unit mass of Fe recovered (Figure 3).
For geochemically scarce metals, however, the form
in which they occur has a major relationship to metal
grade. Above a certain grade, the valuable metal occurs as
a major element in a discrete mineral, and it is only due
to a unique set of ore-forming processes that this grade
threshold is obtained. In the case of Cu occurring above
this grade threshold, one would expect to find Cu occur-
ring as a major element in a discrete Cu-bearing mineral
2000 2010 2020 2030 2040 2050
0
10000
20000
30000
40000
Year
Mining
Recycling
Historical Projected
Figure 1. Historical (pre-2019) and projected zinc supply derived from mining and metal recycling. The
projected scenarios are based on a ‘business as usual’ case. The range in projected Zn demand in 2050 is
also shown. Adapted from Rostek et al. (2023)
Figure 2. Illustration of the relationship between metal abundance and grade for (a) a geochemically abundant metal such as
Fe, and (b) a geochemically scarce metal such as the critical metals. Adapted from Skinner (1976)
Zn
production
(kt/a)
Projected
demand
in2050