1478 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
traditional leach or gold robbing tests allows for a more
comprehensive and accurate assessment of the CM content,
distribution, associations, and influence on the metallurgi-
cal response of complex ores. This paper provides a review
of the advances in the methods for characterization of CM
in complex ores, as well as the application of some of these
methods to a polymetallic deposit.
REVIEW OF METHODOLOGIES
FOR THE CHARACTERIZATION OF
CARBONACEOUS MATTER IN COMPLEX
ORES
An influential investigation by A.S. Radtke and B.J.
Scheiner (1970) explored the involvement of carbona-
ceous matter in gold deposition, highlighting its presence
in both the ore and sedimentary host rocks of the Carlin
deposit. Subsequent research has extensively documented
CM across various sedimentary and meta-sediment hosted
gold deposits, encompassing sediment-hosted disseminated
gold (Carlin-type) and orogenic deposits on a global scale
(Large, Stewart and Maslennikov, 2011 Helm, Vaughan
and Staunton, 2012 Miller, Wan and Diaz, 2016 Hu et
al., 2022).
Numerous metallurgical investigations have explored
the role of CM in gold robbing during ore processing
(Osseo-Asare, Afenya and Abotsi, 1984 Rees and van
Deventer, 2000 Goodall, Leatham and Scales, 2005
Helm, Vaughan and Staunton, 2009 Helm et. al, 2009
Darth et. al, 2020). During these studies, challenges with
CM in gold ores included gold locking within in the matrix
of CM making liberation difficult, and the adsorption of
gold from gold rich solution resulting in low recoveries
(Darth et. al, 2020). Additional investigations revealed
that CM encompasses a variety of organic and inorganic
compounds, with natural carbon, or organic carbon,
identified as the most influential species for gold robbing
(Osseo-Asare, Afenya and Abotsi, 1984 Miller, Wan and
Diaz, 2016). Supplementary studies have further defined
organic carbon, as it can exhibit a combination of amor-
phous and graphitic structures, with a spectrum of crystal
lattice maturities in between (Miller, Wan and Diaz, 2016).
Gold robbing characteristics directly relate to the degree
of disorder of the crystal structure, specifically correlating
with the d-spacing of the carbon structure and inversely
correlated with Lc(002) crystal dimension (Stenebråten
et. al, 1999). Thus, revealing that high disorder within
the crystal structure consistently correlates with a higher
gold robbing capacity (Ng et al., 2022). Despite organic
carbon behaving similarly to activated carbon during cya-
nide leaching (Darth et al., 2020), predicting gold robbing
capacity remains challenging due to the absence of a stan-
dardized estimate for a given concentration of graphitic
carbon found in ore (Helm, Vaughan and Staunton, 2009).
Consequently, the need for further studies on organic
carbon arose to identify the fundamental causes and ulti-
mately predict gold adsorption from cyanide leach solu-
tions, propelling investigations into organic carbon
characterization in mineral processing. Methods such as
elemental analysis (Stenebråten et. al, 1999 van Deventer
et. al, 2005 Hart et. al, 2011 Ren et. al, 2017, Ng et.
al, 2022), optical and electron microscopy (Stenebråten
et. al, 1999 van Deventer et. al, 2005 Hart et. al, 2011
Ng et. al, 2022), X-ray diffraction (XRD) (Stenebråten
et. al, 1999 van Deventer et. al, 2005 Helm et. al, 2009,
Ren et. al, 2017 Ng et. al, 2022), stable carbon isotope
analysis (Hu et. al, 2022), and various spectroscopic tech-
niques including Fourier-transform infrared spectroscopy
(FT-IR) (Stenebråten et. al, 1999 Ng et.al, 2022), Raman
spectroscopy (Stenebråten et. al, 1999 Helm et. al, 2009
Hart et. al, 2011 Ren et. al, 2017 Hu et. al, 2022 Ng
et. al, 2022), near-infrared (NIR)(Olson, 2017), nuclear
magnetic resonance (NMR)( Stenebråten et. al, 1999 Ng
et. al, 2022), X-ray photoelectron spectroscopy (XPS) (van
Deventer et. al, 2005 Ng et.al, 2022), near-edge X-ray
absorption fine structure spectroscopy (NEXAFS)(Ng et.
al, 2022), and diffuse reflectance infrared Fourier transform
(DRIFT) (Ng et. al, 2022) have been employed for organic
carbon characterization and quantification. These studies
have consistently demonstrated a correlation between the
structure of organic carbon, and the degree of disorder in
the crystal lattice, with gold robbing potential (Helm et.
al, 2009 Goodall, Leatham and Scales, 2005 Ren et. al,
2017). Despite the comprehensive array of analytical tech-
niques and characterization methods, accurately predicting
gold robbing capacity remains elusive by these methods.
Mining companies currently utilize different analytical
methods to quantify and predict gold robbing characteris-
tics of gold ores. In one of the methods, the gold robbing
value is a reflection of the cyanide leachable gold of the ore
(AuCN g/t), the final gold concentration after gold robbing
(AuGR g/t) and a 3.4 ppm spike. Values for gold robbing
potential, as estimated by the gold rob number (gold-rob
#),are calculated according to the following equation and
then can be classified from non-gold robbing to highly gold
robbing (Table 1) (Miller, Wan and Diaz, 2016):
Gold-rob #=3.4 g Au/t (spike) +AuCN g/t – AuGR g/t
One of the most capable methods to identify and mea-
sure the degree of crystallinity of carbon is by Raman spec-
troscopy (Helm et. al, 2009 Hart et. al, 2011). Previous
traditional leach or gold robbing tests allows for a more
comprehensive and accurate assessment of the CM content,
distribution, associations, and influence on the metallurgi-
cal response of complex ores. This paper provides a review
of the advances in the methods for characterization of CM
in complex ores, as well as the application of some of these
methods to a polymetallic deposit.
REVIEW OF METHODOLOGIES
FOR THE CHARACTERIZATION OF
CARBONACEOUS MATTER IN COMPLEX
ORES
An influential investigation by A.S. Radtke and B.J.
Scheiner (1970) explored the involvement of carbona-
ceous matter in gold deposition, highlighting its presence
in both the ore and sedimentary host rocks of the Carlin
deposit. Subsequent research has extensively documented
CM across various sedimentary and meta-sediment hosted
gold deposits, encompassing sediment-hosted disseminated
gold (Carlin-type) and orogenic deposits on a global scale
(Large, Stewart and Maslennikov, 2011 Helm, Vaughan
and Staunton, 2012 Miller, Wan and Diaz, 2016 Hu et
al., 2022).
Numerous metallurgical investigations have explored
the role of CM in gold robbing during ore processing
(Osseo-Asare, Afenya and Abotsi, 1984 Rees and van
Deventer, 2000 Goodall, Leatham and Scales, 2005
Helm, Vaughan and Staunton, 2009 Helm et. al, 2009
Darth et. al, 2020). During these studies, challenges with
CM in gold ores included gold locking within in the matrix
of CM making liberation difficult, and the adsorption of
gold from gold rich solution resulting in low recoveries
(Darth et. al, 2020). Additional investigations revealed
that CM encompasses a variety of organic and inorganic
compounds, with natural carbon, or organic carbon,
identified as the most influential species for gold robbing
(Osseo-Asare, Afenya and Abotsi, 1984 Miller, Wan and
Diaz, 2016). Supplementary studies have further defined
organic carbon, as it can exhibit a combination of amor-
phous and graphitic structures, with a spectrum of crystal
lattice maturities in between (Miller, Wan and Diaz, 2016).
Gold robbing characteristics directly relate to the degree
of disorder of the crystal structure, specifically correlating
with the d-spacing of the carbon structure and inversely
correlated with Lc(002) crystal dimension (Stenebråten
et. al, 1999). Thus, revealing that high disorder within
the crystal structure consistently correlates with a higher
gold robbing capacity (Ng et al., 2022). Despite organic
carbon behaving similarly to activated carbon during cya-
nide leaching (Darth et al., 2020), predicting gold robbing
capacity remains challenging due to the absence of a stan-
dardized estimate for a given concentration of graphitic
carbon found in ore (Helm, Vaughan and Staunton, 2009).
Consequently, the need for further studies on organic
carbon arose to identify the fundamental causes and ulti-
mately predict gold adsorption from cyanide leach solu-
tions, propelling investigations into organic carbon
characterization in mineral processing. Methods such as
elemental analysis (Stenebråten et. al, 1999 van Deventer
et. al, 2005 Hart et. al, 2011 Ren et. al, 2017, Ng et.
al, 2022), optical and electron microscopy (Stenebråten
et. al, 1999 van Deventer et. al, 2005 Hart et. al, 2011
Ng et. al, 2022), X-ray diffraction (XRD) (Stenebråten
et. al, 1999 van Deventer et. al, 2005 Helm et. al, 2009,
Ren et. al, 2017 Ng et. al, 2022), stable carbon isotope
analysis (Hu et. al, 2022), and various spectroscopic tech-
niques including Fourier-transform infrared spectroscopy
(FT-IR) (Stenebråten et. al, 1999 Ng et.al, 2022), Raman
spectroscopy (Stenebråten et. al, 1999 Helm et. al, 2009
Hart et. al, 2011 Ren et. al, 2017 Hu et. al, 2022 Ng
et. al, 2022), near-infrared (NIR)(Olson, 2017), nuclear
magnetic resonance (NMR)( Stenebråten et. al, 1999 Ng
et. al, 2022), X-ray photoelectron spectroscopy (XPS) (van
Deventer et. al, 2005 Ng et.al, 2022), near-edge X-ray
absorption fine structure spectroscopy (NEXAFS)(Ng et.
al, 2022), and diffuse reflectance infrared Fourier transform
(DRIFT) (Ng et. al, 2022) have been employed for organic
carbon characterization and quantification. These studies
have consistently demonstrated a correlation between the
structure of organic carbon, and the degree of disorder in
the crystal lattice, with gold robbing potential (Helm et.
al, 2009 Goodall, Leatham and Scales, 2005 Ren et. al,
2017). Despite the comprehensive array of analytical tech-
niques and characterization methods, accurately predicting
gold robbing capacity remains elusive by these methods.
Mining companies currently utilize different analytical
methods to quantify and predict gold robbing characteris-
tics of gold ores. In one of the methods, the gold robbing
value is a reflection of the cyanide leachable gold of the ore
(AuCN g/t), the final gold concentration after gold robbing
(AuGR g/t) and a 3.4 ppm spike. Values for gold robbing
potential, as estimated by the gold rob number (gold-rob
#),are calculated according to the following equation and
then can be classified from non-gold robbing to highly gold
robbing (Table 1) (Miller, Wan and Diaz, 2016):
Gold-rob #=3.4 g Au/t (spike) +AuCN g/t – AuGR g/t
One of the most capable methods to identify and mea-
sure the degree of crystallinity of carbon is by Raman spec-
troscopy (Helm et. al, 2009 Hart et. al, 2011). Previous