42 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
and geostatistics (Deutsch et al., 2023), coupled with key
mineralogical knowledge, ultimately facilitates more sus-
tainable processing of this deposit.
REE CASE STUDY
The REE represent the suite of elements from La to Lu, and
include Y and Sc based on their similar geochemical prop-
erties. These elements find widespread use in numerous
applications, the most important of which for the energy
transition is their usage in electric vehicles and permanent
magnets in wind turbines (IEA, 2022). REE deposits are
broadly divided into those formed through high-temper-
ature (magmatic and hydrothermal) processes, and those
formed through low-temperature (weathering and erosion)
processes (Goodenough et al., 2018). REE derived from
carbonatites (rocks formed through high-temperature mag-
matic processes) are the major contributor to global REE
supply, often consisting of large, high-grade deposits. In
these deposits, discrete REE minerals are the dominant
host of the REE, although some of the REE are also known
to substitute for Ca and P in apatite. The recovery of REE
from discrete REE-bearing minerals such as bastnäsite and
monazite is through a series of mineral processing steps
including gravity, magnetic and electrostatic separation as
well as flotation prior to subsequent leaching and refining
(Jordens et al., 2013). The processing and recovery of these
REE minerals is considered to fall to the right-hand side
of the mineralogical barrier for geochemically scarce metals
(Figure 2a).
Weathered crust elution deposited ion adsorption
clay deposits (IAC) are an alternate source of REE. These
deposits are typically low grade (4000 ppm) and formed
through weathering and alteration processes in humid
environments that mobilised the REE from their primary
minerals (Wu et al., 2023). The REE were subsequently
adsorbed onto clay minerals such as kaolinite or halloysite
(a hydrated form of kaolinite) that can be readily recovered
by in-situ leaching processes with simple monovalent salt
solutions at ambient temperatures. Although the overall
recovery may be low, the relative ease of the recovery and
low processing costs, make this an attractive deposit type
(Moldoveanu and Papangelakis, 2016). IAC ores also show
enrichment in the heavy REE (Sm-Lu and Y) that are cur-
rently in high demand. These deposits are considered to
fall to the left-hand side of the mineralogical barrier for
geochemically scarce metals (Figure 2b). However, they do
not fit Figure 3 in terms of their energy demand given these
ores do not need conventional milling and processing steps.
Here perhaps, the mineralogical barrier could be rather more
philosophically considered with respect to how the mining
and processing should be carried out to avoid the environ-
mental degradation commonly associated with these ores
in China (Yang et al., 2013). There has been much interest
in these ores in the West since China’s threatened ban on
exporting REE metals in the early 2000s. Here, a case study
Figure 5. Illustration of the geometallurgical block model indicating the range in sphalerite composition across the Gamsberg
North deposit. Reproduced with permission from Price et al. (2023)
and geostatistics (Deutsch et al., 2023), coupled with key
mineralogical knowledge, ultimately facilitates more sus-
tainable processing of this deposit.
REE CASE STUDY
The REE represent the suite of elements from La to Lu, and
include Y and Sc based on their similar geochemical prop-
erties. These elements find widespread use in numerous
applications, the most important of which for the energy
transition is their usage in electric vehicles and permanent
magnets in wind turbines (IEA, 2022). REE deposits are
broadly divided into those formed through high-temper-
ature (magmatic and hydrothermal) processes, and those
formed through low-temperature (weathering and erosion)
processes (Goodenough et al., 2018). REE derived from
carbonatites (rocks formed through high-temperature mag-
matic processes) are the major contributor to global REE
supply, often consisting of large, high-grade deposits. In
these deposits, discrete REE minerals are the dominant
host of the REE, although some of the REE are also known
to substitute for Ca and P in apatite. The recovery of REE
from discrete REE-bearing minerals such as bastnäsite and
monazite is through a series of mineral processing steps
including gravity, magnetic and electrostatic separation as
well as flotation prior to subsequent leaching and refining
(Jordens et al., 2013). The processing and recovery of these
REE minerals is considered to fall to the right-hand side
of the mineralogical barrier for geochemically scarce metals
(Figure 2a).
Weathered crust elution deposited ion adsorption
clay deposits (IAC) are an alternate source of REE. These
deposits are typically low grade (4000 ppm) and formed
through weathering and alteration processes in humid
environments that mobilised the REE from their primary
minerals (Wu et al., 2023). The REE were subsequently
adsorbed onto clay minerals such as kaolinite or halloysite
(a hydrated form of kaolinite) that can be readily recovered
by in-situ leaching processes with simple monovalent salt
solutions at ambient temperatures. Although the overall
recovery may be low, the relative ease of the recovery and
low processing costs, make this an attractive deposit type
(Moldoveanu and Papangelakis, 2016). IAC ores also show
enrichment in the heavy REE (Sm-Lu and Y) that are cur-
rently in high demand. These deposits are considered to
fall to the left-hand side of the mineralogical barrier for
geochemically scarce metals (Figure 2b). However, they do
not fit Figure 3 in terms of their energy demand given these
ores do not need conventional milling and processing steps.
Here perhaps, the mineralogical barrier could be rather more
philosophically considered with respect to how the mining
and processing should be carried out to avoid the environ-
mental degradation commonly associated with these ores
in China (Yang et al., 2013). There has been much interest
in these ores in the West since China’s threatened ban on
exporting REE metals in the early 2000s. Here, a case study
Figure 5. Illustration of the geometallurgical block model indicating the range in sphalerite composition across the Gamsberg
North deposit. Reproduced with permission from Price et al. (2023)