XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1483
and other dense minerals. During heavy liquid separation,
samples were filtered at 25 µm and again at 0.45 µm, result-
ing in a 0.45–25 µm fraction and a 25–150 µm fraction.
The filtered solids were placed onto a double-sided
sticky carbon tape on top of a glass slide for SEM analy-
sis. Examinations were completed under variable pressure
(0.5 torr) avoiding the need to coat the samples with con-
ductive material/metals needed to reduce electric charging.
Samples were manually scanned to identify CM grains and
subsequently analyzed optically using a Keyence VHX-
2000 digital microscope (Figure 5). Once images and loca-
tions of grains were logged, the material was submitted for
Raman analyses for carbon characterization.
A ThermoScientific DXR Raman Microscope was used
to characterize individual grains of CM in each sample.
A 532 nm laser with full resolution grating was focused
through a 50× objective on the grains of CM. Spectra were
collected from all identifiable grains of CM within a sam-
ple (1–12 grains) to capture any variation in the degree of
disorder. Raman analysis was also conducted on a sample
of natural graphite and activated carbon to provide rep-
resentative endmember spectra for highly-ordered crystal-
line carbon and disordered amorphous carbon, respectively
(Figure 6). The first-order Raman spectra of CM are
defined by a D band at ~1,330 cm–1 and a dominant G
band at ~1,600 cm–1. Figure 6 illustrates that as the degree
of disorder increases, there is a corresponding broadening
and decrease in intensity of the G band while the D band
broadens and increases in intensity. Crystalline CM also has
a second-order S band at ~2,700 cm–1.
The spectra for individual grains of CM were averaged
for each sample and shown in Figures 7 and 8. In the low
Figure 5. Back-scattered electron image (left) and optical micrograph (right) of CM
Figure 6. Raman spectra for crystalline carbon and amorphous carbon endmembers
and other dense minerals. During heavy liquid separation,
samples were filtered at 25 µm and again at 0.45 µm, result-
ing in a 0.45–25 µm fraction and a 25–150 µm fraction.
The filtered solids were placed onto a double-sided
sticky carbon tape on top of a glass slide for SEM analy-
sis. Examinations were completed under variable pressure
(0.5 torr) avoiding the need to coat the samples with con-
ductive material/metals needed to reduce electric charging.
Samples were manually scanned to identify CM grains and
subsequently analyzed optically using a Keyence VHX-
2000 digital microscope (Figure 5). Once images and loca-
tions of grains were logged, the material was submitted for
Raman analyses for carbon characterization.
A ThermoScientific DXR Raman Microscope was used
to characterize individual grains of CM in each sample.
A 532 nm laser with full resolution grating was focused
through a 50× objective on the grains of CM. Spectra were
collected from all identifiable grains of CM within a sam-
ple (1–12 grains) to capture any variation in the degree of
disorder. Raman analysis was also conducted on a sample
of natural graphite and activated carbon to provide rep-
resentative endmember spectra for highly-ordered crystal-
line carbon and disordered amorphous carbon, respectively
(Figure 6). The first-order Raman spectra of CM are
defined by a D band at ~1,330 cm–1 and a dominant G
band at ~1,600 cm–1. Figure 6 illustrates that as the degree
of disorder increases, there is a corresponding broadening
and decrease in intensity of the G band while the D band
broadens and increases in intensity. Crystalline CM also has
a second-order S band at ~2,700 cm–1.
The spectra for individual grains of CM were averaged
for each sample and shown in Figures 7 and 8. In the low
Figure 5. Back-scattered electron image (left) and optical micrograph (right) of CM
Figure 6. Raman spectra for crystalline carbon and amorphous carbon endmembers