Characterisation and Metallurgical Response of Gold Ores from Transition Zones in Ashanti Belt Zone of Ghana

Francis Kwaku Darteh; Kojo Twum Konadu; Grace Ofori-Sarpong Akuffo; Richard Kwasi Amankwah

doi:doi:10.11648/j.ijmpem.20251001.12

Research Article |

| Peer-Reviewed

Characterisation and Metallurgical Response of Gold Ores from Transition Zones in Ashanti Belt Zone of Ghana

Francis Kwaku Darteh^*

, Kojo Twum Konadu

, Grace Ofori-Sarpong Akuffo

, Richard Kwasi Amankwah

Published in International Journal of Mineral Processing and Extractive Metallurgy (Volume 10, Issue 1)

Received: 15 July 2025 Accepted: 29 July 2025 Published: 18 August 2025

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Abstract

The complex and variable mineralogical compositions of transitional gold ore zones pose significant metallurgical challenges. Using a multi-technique analytical approach that integrates geological, mineralogical, and metallurgical data, this study characterises gold ores from transitional zones within Ghana's Ashanti Belt. XRD, light microscopy, XRF, Raman spectroscopy, sulphur and carbon speciation, preg-robbing index (PRI) tests, and diagnostic leaching studies were performed on six representative samples from three mining companies. The results show that the ores, which are mainly rich in quartz and sericite, have variable sulphide (0.11-0.94%) and organic carbon (0.13-2.11%) contents, which significantly affect the cyanidation performance. Raman spectroscopy revealed different levels of carbon maturity, while optical microscopy verified the presence of pyrite and arsenopyrite. Diagnostic leaching showed highly variable gold deportment: gold was distributed among free-milling phases, sulphides, carbonaceous materials (CM), and residual fines. Samples with higher sulphide and organic carbon contents demonstrated strong preg-robbing behaviour and poor cyanide leach recoveries (34-40%), while those with lower contents achieved recoveries of 75-77%. The study highlights the pronounced intra- and inter-sample variability across the transitional zone ores, underlining the inadequacy of conventional processing approaches. It concludes that a geometallurgical framework anchored in integrated multi-technique characterisation is essential for optimising gold recovery and guiding efficient, domain-specific processing strategies for transitional gold ore deposits.

Published in	International Journal of Mineral Processing and Extractive Metallurgy (Volume 10, Issue 1)
DOI	10.11648/j.ijmpem.20251001.12
Page(s)	27-37
Creative Commons	This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.
Copyright	Copyright © The Author(s), 2025. Published by Science Publishing Group

Keywords

Geometallurgy, Transition Zone, Variability, Gold Ore, Recoveries

1. Introduction

The Ashanti Belt in Ghana represents one of the world’s most prolific gold provinces, forming part of the Paleoproterozoic Birimian terrane that has produced over 150 million ounces of gold historically

[1, 2]

. This structurally complex belt hosts a variety of gold deposit types, including quartz vein-hosted, disseminated sulphide, and shear zone-related mineralisation, with ore characteristics showing significant variability across different geological domains

[3, 4]

. Of particular interest are transitional zones where lithological contacts, alteration boundaries, and structural discontinuities create sharp gradients in ore mineralogy and metallurgical properties.

Transition gold ore zones represent an intermediate stage between oxide and sulphide mineralisation

[5]

. These zones are characterised by partially oxidised minerals and highly variable geochemical compositions, which complicate metallurgical behaviour and recovery efficiency

[6]

. The ore types from transition zones often contain a mixture of oxide minerals, sulphides, and organic carbon phases, leading to unpredictable processing behaviour. This heterogeneity necessitates a detailed and systematic characterisation of ores to understand their mineralogical framework, gold deportment, and response to metallurgical treatment. Studies have demonstrated that transition gold ores frequently exhibit variable gold deportment between free-milling and refractory occurrences, complex sulphide mineral assemblages affecting cyanidation efficiency, and gangue mineral variations impacting comminution and reagent consumption

[7]

These characteristics not only introduce variability in processing outcomes but also necessitate the adoption of advanced geometallurgical frameworks to optimise metallurgical recovery and guide resource management

, 9]. Geometallurgy has emerged as a critical discipline for understanding such complex ore systems, integrating geological, mineralogical, and metallurgical data to optimise resource utilisation

[10, 11]

. The geometallurgical approach is particularly valuable in transition zones where conventional grade-based domaining often fails to capture critical process-relevant characteristics

[12]

. By combining geological, mineralogical, and metallurgical datasets, geometallurgical models enable better predictions of ore behaviour and allow for the implementation of tailored processing strategies across ore domains

[9]

The current study focused on and sought to elucidate intra- and inter-sample variability. This included the identification of mineralogical assemblages, quantification of carbon and sulphur content, and analysis of preg-robbing potential, all of which significantly influence metallurgical recovery in transition zone ores

[13]

Modern geometallurgical characterisation employs a multi-technique analytical approach to address these challenges

[14]

. Hence, this study utilised analytical techniques including X-ray diffraction (XRD), Raman spectroscopy, and LECO elemental analysis (carbon and sulphur) to determine the mineralogical and chemical characteristics of transition gold ores from three gold mines in the Ashanti Belt. These were further linked to metallurgical performance metrics such as cyanide leach recovery, gold deportment, and preg-robbing index (PRI). Such a holistic framework provides the basis for developing predictive models that can delineate this ore type and prescribe optimal processing routes, thereby enhancing economic performance and sustainability.

2. Materials and Methods

2.1. Sample Preparation

Six (6) transition zone samples were collected from 3 different gold mining companies that mine in the Ashanti belt of Ghana. These mining companies were strategically chosen based on their respective locations on the belt (North, middle and south regions of the Ashanti belt). This was in an attempt to capture the variability across the belt. The representative samples from the bulk rock samples were crushed and pulverised to 80% passing 75 µm using the jaw, cone, and roll crushers as well as the ball mill at the Minerals Engineering laboratory of the University of Mines and Technology, UMaT, Tarkwa.

2.2. Chemical and Mineralogical Characterisation

Chemical analysis of the pulverised samples was carried out using the X-ray fluorescence spectroscopy (XRF, Rigaku, ZSX Primus II, Japan). Mineralogical analysis for minerals identification was performed by X-Ray Diffractometer (Bruker D2 Phaser, Germany) using the powder method with Cu kα radiation (1.54060 Å) within 2θ range of 5-80°.

Using polished section on the rock samples, light microscopic analysis (Leitz optical microscope) was used to analyse the occurrence and association of minerals in each sample.

Sulphur and carbon speciation analysis was carried out using the LECO (SC832). LECO analysis uses infrared absorption and thermal conductivity to measure combustion gases within a metallic sample. This process determines the presence and concentration of carbon and sulphur. LECO analysis converts the elements from a sample into their oxidised form by utilising the combustion method (Carbon and Sulphur).

Raman spectroscopy was conducted on the samples to confirm the presence and maturity of carbonaceous material (CM) using Raman spectrometry (532 nm, JASCO, NRS-3100, Japan). Raman spectroscopy (RS) relies on the inelastic scattering of light, wherein incident excitation radiation interacts with most molecules, resulting in a shift in the energy of the incident photon equivalent to the internal vibrational energy

[15, 16]

2.3. Pre-robbing Index (PRI) Test

A 500-g each of the pulverised samples was subjected to PRI test to determine the extent of preg-robbing by contacting each sample with 500 ml of 10 ppm standard gold solution which was prepared by dilution 5 ml of reagent grade 1000 ppm standard solution in 495 ml of 100 ppm cyanide solution. The pulps were bottle-rolled for 24 hrs. Solution samples were taken and analysed using the Atomic Adsorption Spectrophotometer (AAS AA-7000 SHIMADZU) at the end of the 24-hr period.

2.4. Diagnostic Leaching

Diagnostic leaching was carried out on 1 kg of each sample at particle size of 80% -75 µm. This comprised of a stage-wise series of cyanidation tests to determine the gold association in the various minerals. Figure 1 describes the details of stages undertaken.

3. Results and Discussion

3.1. Chemical Composition of Ore Samples

The chemical composition of the six analysed samples (R 1, R 2, LG, AG-B, AG-E, BB) in Table 1 revealed significant variations in oxide and elemental content. The major components were SiO₂ (53.64-64.32%) and Al₂O₃ (15.45-25.01%), which may be in accordance with silicate-rich ores, possibly containing quartz, feldspars, and clay minerals. The iron content, expressed as Fe₂O₃ (3.11-7.49%), suggests the presence of iron oxides and/or sulphides, which could affect cyanidation efficiency if reactive minerals like pyrite are present. CaO, MgO and TiO were also found in their respective wt%. The composition noted as others refers to the trace elements and loss on ignition resulting from volatile constituents of each sample.

Of note are the considerable variability in carbon (C) and sulphur (S) (Table 2). R1 had the most C (3.61%) and S (1.22%) and may represent carbonaceous materials or organic materials capable of preg-robbing gold in leaching circuits. AG-B and AG-E had the least C (0.73-0.82%) and S (0.19-0.28%) and can be interpreted to be of a different mineralisation type with less gold recovery problems due to low organic carbon content.

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Figure 1. Stage-wise Diagnostic Leaching Process.

Gold grades ranged from 0.64 g/t (LG) to 2.12 g/t (AG-E). AG-E (2.12 g/t) and AG-B (1.84 g/t) contained the highest gold values, despite having lower carbon and sulphur. This may suggest that gold may be associated with non-refractory phases, making these samples potentially more amenable to conventional cyanidation.

3.2. Mineralogical Characterisation

3.2.1. Petrographic Analysis

Results from the optical microscopic analysis for the various samples analysed (as shown in figure 2) indicated the presence of iron sulphides (most predominantly pyrite). Samples from MINE A (R1, R2, LG) showed pyrite as the only iron sulphide mineral present in the samples. R1 showed some euhedral and sub-hedral pyrite formed with some deformations. The deformations may be due to alterations resulting from partial oxidation by virtue of its exposure in the transition zone

[17]

. According to Dilles and John

[18]

, pyrites are more susceptible to weathering than other sulphides like chalcopyrite hence such deformations are likely to be seen in transition zones. This altered pyrite may oxidise into iron oxides of hematite and magnetite depending on the degree of oxidation and alteration

[19, 20]

. Samples from R2 and LG analysed showed similar properties with R2 showing some anhedral pyrite which are disseminated. LG on the other hand showed pyrite which seemed to have formed within foliated planes but infoliated. From Mine B, AG-B under the microscope showed some pyrite and arsenopyrite. Intergrowths of arsenopyrite in pyrite were observed. Again, there were some forms of deformation of the sulphide minerals into oxides of iron.

Most significantly, the presence of gold was observed conspicuously under the microscope, attached (but not occluded) in the arsenopyrite mineral. This could indicate some liberation of gold in this sample. AG-E, on the other hand, showed the presence of pyrite and arsenopyrite. Most of the pyrite present appeared to be euhedral and slightly deformed. Sample from Mine C, however, showed a similar characteristic of the euhedral and sub-hedral pyrite present in the sample.

3.2.2. XRD Analysis

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Figure 2. Optical Images of Polished Rock Samples Under Reflected Light for Samples from Mine A (R1, R2, LG), Mine B (AG-B, AG-E) and Mine C (BB).

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Figure 3. X-ray Diffraction Pattern of the Samples from the Various Mines (Mine A - R1, R2, LG; Mine B - AG-B, AG-E; Mine C - BB).

Characterisation by XRD revealed quartz, albite and muscovite for all samples from all the mines (A, B, C). R2 and LG from mine A exhibited the presence of kaolinite while AG-E and AG-B from mine B also exhibited the presence of dolomite and chlorite (AG-E). Geochemically, kaolinite can adsorb gold complexes from solution, contributing to preg-robbing behaviour

[21]

. BB from mine C rather had chlorite and gypsum present as indicated in Figure 3. Indications project that there are alterations of plagioclase feldspar (albite) into sericites in the form of muscovite, kaolinite and chlorites

[22]

. Sericite is a frequently occurring mineral that forms as a result of changes in orthoclase or plagioclase feldspars in regions that have seen hydrothermal alteration, often linked to copper, tin, or other hydrothermal metal deposits. According to Dilles and John

[18]

, the substitution of feldspars and mafic silicates with muscovite, abundant pyrite or hematite (1-5 vol%), and chlorite is a prevalent process that leads to sericitic alteration.

Table 1. Chemical Composition of Ores from the Various Geological Settings.

	CHEMICAL COMPOSITION, %
	MgO	CaO	Al₂O₃	SiO₂	K₂O	TiO₂	Fe₂O₃	Others	Au^{^} (g/t)
R 1	1.24	3.08	17.34	56	1.93	0.5	5.8	9.29	1.07
R 2	0.4	0.35	22.55	58.43	2.62	0.64	4.54	7.26	1.22
LG	0.54	0.13	25.01	55.51	2.86	0.76	3.77	8.83	0.64
AG - B	0.52	3.06	16.43	64.32	2.14	0.24	3.11	9.18	1.84
AG - E	0.52	2.6	15.45	64.22	2.04	0.24	3.14	10.78	2.12
BB	0.4	0.37	24.72	53.64	2.63	0.82	7.49	7.31	1.07

^Analysis by Fire Assay

Sericites are typical characteristics of ores from transition zones

[23]

hence evidence of the ores coming from the transitional zones. These occurrences are seen from the ores from all the mine sites, hence, suggesting substantial supergene alteration. Sillitoe

[24]

reported similar mineralogy in the ore from the supergene zone (transitional zone) of VHMS deposits from the South Urals.

Table 2. Sulphur and Carbon Speciation Analysis by LECO.

Sample ID		Total Sulphur (%)	Sulphide Sulphur (%)	Total Carbon (%)	Organic Carbon (%)
Mine A	R1	1.22	0.93	3.61	2.11
	R2	1.23	0.91	1.98	1.48
	LG	1.16	0.94	1.42	1.35
Mine B	AG-B	0.19	0.11	0.82	0.15
Mine B	AG-E	0.28	0.21	0.73	0.13
Mine C	BB	0.78	0.73	1.83	1.67

3.3. Evidence of Sulphide and Carbon Presence and Their Implications

Results presented in Table 2 indicates that the sulphide content ranges from 0.11 - 0.94% with an organic carbon content of 0.13 - 2.11%. Sulphide sulphur and organic content in samples from Mine A were very high (0.91-0.94% and 1.42 -3.61% respectively). Sample from Mine C also had high content of sulphide sulphur (0.73%) and organic carbon (1.83%). Very low value of sulphur and carbon, however, were recorded for samples from Mine B. The high content of sulphur and carbon can present serious operational challenges during gold recovery by cyanidation.

Results of preg-robbing index (PRI) analysis conducted on the samples as shown in figure 4 indicated that samples from Mine A and C had high PRI (>60%). Evidently, the high content of organic matter present in the samples may account for the high PRI although the maturity of the carbon also plays a very significant role. Samples from Mine B, however, showed minimal PRI obviously due to the low content of organic matter.

The results obtained correlates with the peaks shown by Raman spectroscopic analysis (Figure 5). In recent years, Raman spectroscopy has supplanted X-ray diffraction (XRD) as the method of choice for investigating these naturally occurring CM. In this study, Raman spectroscopy was utilised to further confirm the presence of carbonaceous matter in each of the samples from the various mines. The D (Disordered) peak and G (Graphitic) peak which are characteristic of CM

[25-27]

appeared in samples from Mine A and Mine C at 1350 cm^-1 and 1580 cm^-1 respectively. R1 and R2 from Mine A had the most prominent peaks. This correlates and confirms the results obtained from LECO and the PRI test. AG-E and AG-B (Mine B) displays nearly featureless spectrum with weak and poorly resolved D and G peaks, indicating an extremely low concentration of carbonaceous material. This could explain the low PRI value obtained and confirm the low carbon contents as revealed by LECO analysis for the samples. These observations are consistent with the findings of several researches that demonstrated that carbon maturity and ordering affect preg-robbing potential

[26, 28-30]

. Carbon maturity in gold ores significantly impacts preg-robbing with more mature carbon, like activated carbon and charcoal exhibiting stronger preg-robbing behaviour than less mature carbon, such as wood chips. This is because mature carbonaceous materials have a more developed graphitic structure with a larger surface area and pore volume, providing more sites for gold adsorption. The broadening of the D and G bands is indicative of an increase in disorder within the graphite structure, while variations in the shape and intensity of these bands reflect changes in disorder and crystallite size

[28]

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Figure 4. Preg-robbing Index and Organic Carbon Content of Various Samples from each Mine.

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Figure 5. Raman Spectra of the Samples from Various Mines.

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Figure 6. Deportment of Gold following each Cyanidation Stage.

3.4. Metallurgical Response of Transition Ores

Gold Deportment Studies

Diagnostic leaching is a powerful analytical tool for determining the gold-to-mineral-phase ratio in any ore. It is useful in identifying and characterising unexplored ores and resolving metallurgical issues in well-characterised ores

[31]

The results of the diagnostic leaching of the ore are illustrated in Figure 6. The preliminary cyanide leaching of untreated ore yielded a gold extraction of 34-36% for samples from Mine A, whereas samples from Mine B exhibited recoveries of 75-77%. A recovery of 40.32% was obtained for the sample from Mine C, signifying extremely low cyanide-recoverable gold for Mines A and C. The gold in the samples from Mines A and C was primarily linked with sulphides and carbonaceous material (CM). Approximately 22-27% of the gold in samples from Mine A was located within the sulphides, whereas 33.22% of the gold in samples from Mine C was identified in the sulphides. Approximately 11-15% was occluded in sulphides for samples from Mine B. For gold associated with CM, 12.3% was reported for Mine C, 15-26% for Mine A, and < 2% for Mine B. This aligns with the low PRI values, carbon speciation study, and Raman spectroscopic analysis obtained from samples at Mine B. The residual gold values in the final tailings for Mine A and C were 14-20% and 13.6%, respectively, whereas Mine B recorded 7%. Samples from Mine B are more susceptible to cyanide leaching than those from Mine A and C, where gold is predominantly encapsulated in sulphides and carbonaceous material.

Samples AG-B and AG-E appear to represent more oxidised transitional facies, with gold dominantly present in free-milling form and projects minimal influence from sulphide encapsulation or preg-robbing constituents. Conversely, R1, R2, and LG are more refractory, characterised by higher sulphide-bound and carbon-bound gold, which may necessitate additional pre-treatment strategies for improved metallurgical performance.

4. Conclusions

The chemical, mineralogical characterisation and metallurgical characterisation of gold ores from transitional zones within the Ashanti Belt of Ghana highlight the complex and highly variable nature of these ore bodies. Chemical analyses revealed significant fluctuations in carbon and sulphur content across samples, with elevated organic carbon and sulphide sulphur levels particularly noted in ores from Mines A and C. These geochemical attributes are strongly correlated with high preg-robbing indices (PRI) and reduced cyanide leach recoveries, highlighting the refractory nature of the gold in these domains.

Mineralogical studies through XRD, optical microscopy, and Raman spectroscopy confirmed the presence of quartz, sericite, kaolinite, and sulphide minerals such as pyrite and arsenopyrite, all of which influence gold recovery behaviour. Notably, samples with abundant carbonaceous matter and sulphide minerals exhibited stronger resistance to cyanidation, necessitating alternative or pre-treatment strategies to improve gold liberation and extraction.

Diagnostic leaching studies provided crucial insights into gold deportment, illustrating that a substantial proportion of the gold is associated with sulphides and carbonaceous material in more refractory samples. In contrast, samples from Mine B, with lower carbon and sulphur content, demonstrated better cyanide leach recoveries and less preg-robbing, highlighting the heterogeneity even within transitional zones.

This study reaffirms that the transitional zone ores cannot be treated uniformly with conventional methods. Their mineralogical and geochemical variability demands a geometallurgical approach that integrates geological, mineralogical, and metallurgical datasets. Modern geometallurgical frameworks, through multi-technique characterisation and predictive modeling, offer a pathway to optimize resource management, delineate ore domains more accurately, and design tailored processing strategies that maximise gold recovery and economic returns.

Ultimately, the findings emphasize the need for continuous, integrated ore characterisation programs in transitional zones to inform metallurgical decision-making. The incorporation of this detailed dataset into a geometallurgical model will not only improve predictive control over processing outcomes but also support the sustainable and efficient exploitation of gold resources in the Ashanti Belt and similar mineralised terrains.

Abbreviations

XRD	X-ray Diffractometer
PRI	Preg-robbing Index
XRF	X-ray Flourescence
RS	Raman Spectroscopy
CM	Carbonaceous Material
S	Sulphur
C	Carbon
D peak	Disordered Peak
G peak	Graphitic Peak

Acknowledgments

The authors acknowledge the assistance of all the teaching and research assistants of the minerals engineering department of the University of Mines and Technology.

Author Contributions

Francis Kwaku Darteh: Conceptualization, Investigation, Formal Analysis, Writing - original draft

Kojo Twum Konadu: Methodology, Resources, Supervision

Grace Ofori-Sarpong Akuffo: Supervision, Validation, Writing - review & editing

Richard Kwasi Amankwah: Supervision, Validation, Writing - review & editing

Data Availability Statement

The data supporting the outcome of this research work has been reported in this manuscript.

Funding

This work was supported by the University of Mines and Technology - Staff Development Programme and the Ghana Chamber of Mines - Tertiary Education fund (UMaT-Gh_Chamber_of_Mines-Pg/011/22).

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	H. E. Frimmel, “Earth’s continental crustal gold endowment,” Earth Planet. Sci. Lett., 2008, https://doi.org/10.1016/j.epsl.2007.11.022
[2]	R.. Goldfarb, D.. Groves, and S. Gardoll, “Orogenic gold and geologic time: a global synthesis,” Ore Geol. Rev., vol. 18, no. 1-2, pp. 1-75, Apr. 2001, https://doi.org/10.1016/S0169-1368(01)00016-6
[3]	A. H. Allibone et al., “Structural Controls on Gold Mineralization at the Ashanti Deposit, Obuasi, Ghana,” in Integrated Methods for Discovery Global Exploration in the Twenty-First Century, Society of Economic Geologists, 2002. https://doi.org/10.5382/SP.09.04
[4]	S. Perrouty, L. Aillères, M. W. Jessell, L. Baratoux, Y. Bourassa, and B. Crawford, “Revised Eburnean geodynamic evolution of the gold-rich southern Ashanti Belt, Ghana, with new field and geophysical evidence of pre-Tarkwaian deformations,” Precambrian Res., 2012, https://doi.org/10.1016/j.precamres.2012.01.003
[5]	K. Adomako-Ansah, A. Boateng, and A. Asante, “Implications of Ore Textures for Gold Recovery at Esaase Deposit, Asanko Gold Mine,” Ghana Min. J., 2022, https://doi.org/10.4314/gm.v22i1.2
[6]	D. Fougerouse et al., “Evidence for two stages of mineralization in West Africa’s largest gold deposit: Obuasi, Ghana,” Econ. Geol., 2017, https://doi.org/10.2113/econgeo.112.1.3
[7]	S. L. Chryssoulis and L. J. Cabri, “Significance of gold mineralogical balances in mineral processing,” Trans. Inst. Min. Metall. Sect. C Miner. Process. Extr. Metall., 1990.
[8]	G. Ofori-Sarpong, T. Okwaisie, and R. K. Amankwah, “Geometallurgical Studies on Gold Ore for Enhanced Comminution and Leaching,” Ghana Min. J., 2019, https://doi.org/10.4314/gm.v19i1.7
[9]	P. Lamberg, “Particles-the bridge between geology and metallurgy,” in Proceedings of Conference in Minerals Engineering (CME), 2011.
[10]	S. R. Williams and J. M. Richardson, “Geometallurgical mapping: a new approach that reduces technical risk geometallurgical mapping,” Sgs Miner. Serv., 2004.
[11]	S. Dominy, L. O’Connor, H. Glass, S. Purevgerel, and Y. Xie, “Towards Representative Metallurgical Sampling and Gold Recovery Testwork Programmes,” Minerals, vol. 8, no. 5, p. 193, May 2018, https://doi.org/10.3390/min8050193
[12]	C. Lund, P. Lamberg, and T. Lindberg, “Practical way to quantify minerals from chemical assays at Malmberget iron ore operations - An important tool for the geometallurgical program,” Miner. Eng., 2013, https://doi.org/10.1016/j.mineng.2013.04.005
[13]	M. Parian, P. Lamberg, and J. Rosenkranz, “Process simulations in mineralogy-based geometallurgy of iron ores,” Miner. Process. Extr. Metall. Trans. Inst. Min. Metall., vol. 130, no. 1, pp. 25-30, 2021, https://doi.org/10.1080/25726641.2018.1507072
[14]	J. Liipo et al., “Geometallurgical characterization of South Georgian complex copper-gold ores,” J. South. African Inst. Min. Metall., vol. 119, no. 4, 2019, https://doi.org/10.17159/2411-9717/565/2019
[15]	D. Kalita, P. Konwar, D. Sahu, S. Baruah, and S. Barua, “Fluoropolymer nanocomposites: introduction, fundamental properties, and high-performance applications,” in Advanced Fluoropolymer Nanocomposites, Elsevier, 2023, pp. 79-120. https://doi.org/10.1016/B978-0-323-95335-1.00023-2
[16]	K. T. Konadu et al., “Enzymatic degradation of carbonaceous matter in contrasting South African refractory gold ores using cell-free spent medium from Phanerochaete chrysosporium,” Hydrometallurgy, 2023, https://doi.org/10.1016/j.hydromet.2023.106087
[17]	D. A. John, T. W. Sisson, G. N. Breit, R. O. Rye, and J. W. Vallance, “Characteristics, extent and origin of hydrothermal alteration at Mount Rainier Volcano, Cascades Arc, USA: Implications for debris-flow hazards and mineral deposits,” J. Volcanol. Geotherm. Res., vol. 175, no. 3, pp. 289-314, Aug. 2008, https://doi.org/10.1016/j.jvolgeores.2008.04.004
[18]	J. H. Dilles and D. A. John, “Porphyry and Epithermal Mineral Deposits,” in Encyclopedia of Geology: Volume 1-6, Second Edition, 2020. https://doi.org/10.1016/B978-0-08-102908-4.00005-9
[19]	G. Hu, K. Dam-Johansen, S. Wedel, and J. P. Hansen, “Decomposition and oxidation of pyrite,” 2006. https://doi.org/10.1016/j.pecs.2005.11.004
[20]	L. Liu, Q. Liu, S. Zhang, Y. Li, and L. Yang, “The thermal transformation behavior and products of pyrite during coal gangue combustion,” Fuel, 2022, https://doi.org/10.1016/j.fuel.2022.124803
[21]	J. Tremolada, R. Dzioba, A. Bernardo-Sánchez, and J. M. Menéndez-Aguado, “The preg-robbing of gold and silver by clays during cyanidation under agitation and heap leaching conditions,” Int. J. Miner. Process., 2010, https://doi.org/10.1016/j.minpro.2009.12.001
[22]	W. A. Deer, R. A. Howie, and J. Zussman, An Introduction to the Rock-Forming Minerals. Mineralogical Society of Great Britain and Ireland, 2013. https://doi.org/10.1180/DHZ
[23]	R. H. Sillitoe, “Porphyry copper systems,” Econ. Geol., 2010, https://doi.org/10.2113/gsecongeo.105.1.3
[24]	E. V. Belogub, K. A. Novoselov, V. A. Yakovleva, and B. Spiro, “Supergene sulphides and related minerals in the supergene profiles of VHMS deposits from the South Urals,” Ore Geol. Rev., vol. 33, no. 3-4, pp. 239-254, Jun. 2008, https://doi.org/10.1016/j.oregeorev.2006.03.008
[25]	S. S. Dimov and B. R. Hart, “Applications of microbeam analytical techniques in gold deportment studies and characterization of losses during the gold recovery process,” Surf. Interface Anal., vol. 49, no. 13, pp. 1404-1415, Dec. 2017, https://doi.org/10.1002/sia.6287
[26]	K. T. Konadu, S. T. L. Harrison, K. Osseo-Asare, and K. Sasaki, “Transformation of the carbonaceous matter in double refractory gold ore by crude lignin peroxidase released from the white-rot fungus,” Int. Biodeterior. Biodegradation, vol. 143, p. 104735, Sep. 2019, https://doi.org/10.1016/j.ibiod.2019.104735
[27]	N. Cheng, J. Pan, M. Shi, Q. Hou, and Y. Han, “Using Raman spectroscopy to evaluate coal maturity: The problem,” 2022. https://doi.org/10.1016/j.fuel.2021.122811
[28]	O. Beyssac, J. N. Rouzaud, and B. Goffe, “Raman spectroscopy of carbonaceous matter: Comparison between natural samples and experimental products,” Acta Univ. Carolinae, Geol., 2002.
[29]	G. Ofori-Sarpong, M. Tien, and K. Osseo-Asare, “Myco-hydrometallurgy: Coal model for potential reduction of preg-robbing capacity of carbonaceous gold ores using the fungus, Phanerochaete chrysosporium,” Hydrometallurgy, 2010, https://doi.org/10.1016/j.hydromet.2010.02.007
[30]	G. Ofori-Sarpong, K. Osseo-Asare, and M. Tien, “Mycohydrometallurgy: Biotransformation of double refractory gold ores by the fungus, Phanerochaete chrysosporium,” Hydrometallurgy, vol. 137, pp. 38-44, May 2013, https://doi.org/10.1016/j.hydromet.2013.05.003
[31]	W. R. Goodall, P. J. Scales, and A. R. Butcher, “The use of QEMSCAN and diagnostic leaching in the characterisation of visible gold in complex ores,” Miner. Eng., vol. 18, no. 8, pp. 877-886, Jul. 2005, https://doi.org/10.1016/j.mineng.2005.01.018

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Darteh, F. K., Konadu, K. T., Akuffo, G. O., Amankwah, R. K. (2025). Characterisation and Metallurgical Response of Gold Ores from Transition Zones in Ashanti Belt Zone of Ghana. International Journal of Mineral Processing and Extractive Metallurgy, 10(1), 27-37. https://doi.org/10.11648/j.ijmpem.20251001.12

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Darteh, F. K.; Konadu, K. T.; Akuffo, G. O.; Amankwah, R. K. Characterisation and Metallurgical Response of Gold Ores from Transition Zones in Ashanti Belt Zone of Ghana. Int. J. Miner. Process. Extr. Metall. 2025, 10(1), 27-37. doi: 10.11648/j.ijmpem.20251001.12

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AMA Style

Darteh FK, Konadu KT, Akuffo GO, Amankwah RK. Characterisation and Metallurgical Response of Gold Ores from Transition Zones in Ashanti Belt Zone of Ghana. Int J Miner Process Extr Metall. 2025;10(1):27-37. doi: 10.11648/j.ijmpem.20251001.12

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@article{10.11648/j.ijmpem.20251001.12,
  author = {Francis Kwaku Darteh and Kojo Twum Konadu and Grace Ofori-Sarpong Akuffo and Richard Kwasi Amankwah},
  title = {Characterisation and Metallurgical Response of Gold Ores from Transition Zones in Ashanti Belt Zone of Ghana
},
  journal = {International Journal of Mineral Processing and Extractive Metallurgy},
  volume = {10},
  number = {1},
  pages = {27-37},
  doi = {10.11648/j.ijmpem.20251001.12},
  url = {https://doi.org/10.11648/j.ijmpem.20251001.12},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ijmpem.20251001.12},
  abstract = {The complex and variable mineralogical compositions of transitional gold ore zones pose significant metallurgical challenges. Using a multi-technique analytical approach that integrates geological, mineralogical, and metallurgical data, this study characterises gold ores from transitional zones within Ghana's Ashanti Belt. XRD, light microscopy, XRF, Raman spectroscopy, sulphur and carbon speciation, preg-robbing index (PRI) tests, and diagnostic leaching studies were performed on six representative samples from three mining companies. The results show that the ores, which are mainly rich in quartz and sericite, have variable sulphide (0.11-0.94%) and organic carbon (0.13-2.11%) contents, which significantly affect the cyanidation performance. Raman spectroscopy revealed different levels of carbon maturity, while optical microscopy verified the presence of pyrite and arsenopyrite. Diagnostic leaching showed highly variable gold deportment: gold was distributed among free-milling phases, sulphides, carbonaceous materials (CM), and residual fines. Samples with higher sulphide and organic carbon contents demonstrated strong preg-robbing behaviour and poor cyanide leach recoveries (34-40%), while those with lower contents achieved recoveries of 75-77%. The study highlights the pronounced intra- and inter-sample variability across the transitional zone ores, underlining the inadequacy of conventional processing approaches. It concludes that a geometallurgical framework anchored in integrated multi-technique characterisation is essential for optimising gold recovery and guiding efficient, domain-specific processing strategies for transitional gold ore deposits.},
 year = {2025}
}

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TY  - JOUR
T1  - Characterisation and Metallurgical Response of Gold Ores from Transition Zones in Ashanti Belt Zone of Ghana

AU  - Francis Kwaku Darteh
AU  - Kojo Twum Konadu
AU  - Grace Ofori-Sarpong Akuffo
AU  - Richard Kwasi Amankwah
Y1  - 2025/08/18
PY  - 2025
N1  - https://doi.org/10.11648/j.ijmpem.20251001.12
DO  - 10.11648/j.ijmpem.20251001.12
T2  - International Journal of Mineral Processing and Extractive Metallurgy
JF  - International Journal of Mineral Processing and Extractive Metallurgy
JO  - International Journal of Mineral Processing and Extractive Metallurgy
SP  - 27
EP  - 37
PB  - Science Publishing Group
SN  - 2575-1859
UR  - https://doi.org/10.11648/j.ijmpem.20251001.12
AB  - The complex and variable mineralogical compositions of transitional gold ore zones pose significant metallurgical challenges. Using a multi-technique analytical approach that integrates geological, mineralogical, and metallurgical data, this study characterises gold ores from transitional zones within Ghana's Ashanti Belt. XRD, light microscopy, XRF, Raman spectroscopy, sulphur and carbon speciation, preg-robbing index (PRI) tests, and diagnostic leaching studies were performed on six representative samples from three mining companies. The results show that the ores, which are mainly rich in quartz and sericite, have variable sulphide (0.11-0.94%) and organic carbon (0.13-2.11%) contents, which significantly affect the cyanidation performance. Raman spectroscopy revealed different levels of carbon maturity, while optical microscopy verified the presence of pyrite and arsenopyrite. Diagnostic leaching showed highly variable gold deportment: gold was distributed among free-milling phases, sulphides, carbonaceous materials (CM), and residual fines. Samples with higher sulphide and organic carbon contents demonstrated strong preg-robbing behaviour and poor cyanide leach recoveries (34-40%), while those with lower contents achieved recoveries of 75-77%. The study highlights the pronounced intra- and inter-sample variability across the transitional zone ores, underlining the inadequacy of conventional processing approaches. It concludes that a geometallurgical framework anchored in integrated multi-technique characterisation is essential for optimising gold recovery and guiding efficient, domain-specific processing strategies for transitional gold ore deposits.
VL  - 10
IS  - 1
ER  -

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Author Information

Francis Kwaku Darteh

Minerals Engineering Department, University of Mines and Technology, Tarkwa, Ghana

Biography: Francis Kwaku Darteh is a Post-Graduate Assistant at the Minerals Engineering Department of the University of Mines and Technology, Tarkwa-Ghana. He holds a BSc in Minerals Engineering from University of Mines and Technology, UMaT-Tarkwa, Ghana. His research interest includes recovery of precious metals and extractive metallurgy, geometallurgy, biotechnology and bioremediation techniques, and nanotechnology. He is a member of Society for Mining, Metallurgy and Exploration Engineers (SME) and West African Institute of Mining, Metallurgy and Petroleum (WAIMM).

Research Fields: Precious metals and extractive metallurgy, Geometallurgy, Biotechnology and bioremediation techniques, Nanotechnology

Contact Email

http://orcid.org/0000-0003-2450-621X
Kojo Twum Konadu

Minerals Engineering Department, University of Mines and Technology, Tarkwa, Ghana

Biography: Kojo Twum Konadu is a Lecture in the Minerals Engineering department of the university of mines and technology, Ghana. He holds a PhD in Engineering from Kyushu University, Fukuoka, Japan and a BSc in Minerals Engineering from University of Mines and Technology, UMaT-Tarkwa, Ghana. His research interests include (i) Hydrometallurgy and Biohydrometallurgy of precious and base metals and (ii) Solid characterization.

Research Fields: Hydrometallurgy, Biohydrometallurgy of precious and base metals, Solid characterization

http://orcid.org/0000-0002-7388-5247
Grace Ofori-Sarpong Akuffo

Minerals Engineering Department, University of Mines and Technology, Tarkwa, Ghana

Biography: Grace Ofori-Sarpong Akuffo is a Professor of Minerals Engineering at the University of Mines and Technology, Tarkwa. She holds PhD in Energy and Mineral Engineering from Pennsylvania State University, MSc in Environmental Resources Management and BSc in Metallurgical Engineering, both from the Kwame Nkrumah University of Science and Technology, KNUST, Kumasi, Ghana. She is a Fellow of Ghana Academy of Arts and Sciences and West African Institute of Mining, Metallurgy and Petroleum (WAIMM). She is also a member of the Society for Mining, Metallurgy and Exploration Engineers (SME), Ghana Institution of Engineers and the Founder and President of Ladies in Mining and Allied Professions in Ghana. Her areas of research interest include microbial-mineral interaction, environmental biohydrometallurgy, geometallurgy, acid mine drainage issues and precious minerals beneficiation.

Research Fields: Microbial-mineral interaction, Environmental biohydrometallurgy, Geometallurgy, Acid mine drainage issues, Precious minerals beneficiation

http://orcid.org/0000-0002-9448-4864
Richard Kwasi Amankwah

Minerals Engineering Department, University of Mines and Technology, Tarkwa, Ghana

Biography: Richard Kwasi Amankwah is a professor of Minerals Engi-neering at the University of Mines and Technology (UMaT), Tarkwa, Ghana. He holds a PhD degree in Mining Engineering from Queen’s University, Canada, and MPhil and BSc in Metallurgical Engineering, both from the Kwame Nkrumah University of Science and Technology, KNUST, Kumasi, Ghana. His research in-terests include gold beneficiation, water quality man-agement, microwave processing of minerals, small-scale mining, medical geology, microbial mineral recovery and environmental biotechnology. He is a Fellow of the West African Institute of Mining, Metallurgy and Petroleum (WAIMM), a member of the Ghana Institute of Engineers (GhIE) and Society for Mining and Exploration Engineers.

Research Fields: Gold beneficiation, Water quality management, Microwave processing of minerals, Small-scale mining, medical geology, Microbial mineral recovery, Environmental biotechnology

http://orcid.org/0000-0002-7727-1568

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Plain Text BibTeX RIS

APA Style

Darteh, F. K., Konadu, K. T., Akuffo, G. O., Amankwah, R. K. (2025). Characterisation and Metallurgical Response of Gold Ores from Transition Zones in Ashanti Belt Zone of Ghana. International Journal of Mineral Processing and Extractive Metallurgy, 10(1), 27-37. https://doi.org/10.11648/j.ijmpem.20251001.12

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ACS Style

Darteh, F. K.; Konadu, K. T.; Akuffo, G. O.; Amankwah, R. K. Characterisation and Metallurgical Response of Gold Ores from Transition Zones in Ashanti Belt Zone of Ghana. Int. J. Miner. Process. Extr. Metall. 2025, 10(1), 27-37. doi: 10.11648/j.ijmpem.20251001.12

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AMA Style

Darteh FK, Konadu KT, Akuffo GO, Amankwah RK. Characterisation and Metallurgical Response of Gold Ores from Transition Zones in Ashanti Belt Zone of Ghana. Int J Miner Process Extr Metall. 2025;10(1):27-37. doi: 10.11648/j.ijmpem.20251001.12

Copy | Download

@article{10.11648/j.ijmpem.20251001.12,
  author = {Francis Kwaku Darteh and Kojo Twum Konadu and Grace Ofori-Sarpong Akuffo and Richard Kwasi Amankwah},
  title = {Characterisation and Metallurgical Response of Gold Ores from Transition Zones in Ashanti Belt Zone of Ghana
},
  journal = {International Journal of Mineral Processing and Extractive Metallurgy},
  volume = {10},
  number = {1},
  pages = {27-37},
  doi = {10.11648/j.ijmpem.20251001.12},
  url = {https://doi.org/10.11648/j.ijmpem.20251001.12},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ijmpem.20251001.12},
  abstract = {The complex and variable mineralogical compositions of transitional gold ore zones pose significant metallurgical challenges. Using a multi-technique analytical approach that integrates geological, mineralogical, and metallurgical data, this study characterises gold ores from transitional zones within Ghana's Ashanti Belt. XRD, light microscopy, XRF, Raman spectroscopy, sulphur and carbon speciation, preg-robbing index (PRI) tests, and diagnostic leaching studies were performed on six representative samples from three mining companies. The results show that the ores, which are mainly rich in quartz and sericite, have variable sulphide (0.11-0.94%) and organic carbon (0.13-2.11%) contents, which significantly affect the cyanidation performance. Raman spectroscopy revealed different levels of carbon maturity, while optical microscopy verified the presence of pyrite and arsenopyrite. Diagnostic leaching showed highly variable gold deportment: gold was distributed among free-milling phases, sulphides, carbonaceous materials (CM), and residual fines. Samples with higher sulphide and organic carbon contents demonstrated strong preg-robbing behaviour and poor cyanide leach recoveries (34-40%), while those with lower contents achieved recoveries of 75-77%. The study highlights the pronounced intra- and inter-sample variability across the transitional zone ores, underlining the inadequacy of conventional processing approaches. It concludes that a geometallurgical framework anchored in integrated multi-technique characterisation is essential for optimising gold recovery and guiding efficient, domain-specific processing strategies for transitional gold ore deposits.},
 year = {2025}
}

Copy | Download

TY  - JOUR
T1  - Characterisation and Metallurgical Response of Gold Ores from Transition Zones in Ashanti Belt Zone of Ghana

AU  - Francis Kwaku Darteh
AU  - Kojo Twum Konadu
AU  - Grace Ofori-Sarpong Akuffo
AU  - Richard Kwasi Amankwah
Y1  - 2025/08/18
PY  - 2025
N1  - https://doi.org/10.11648/j.ijmpem.20251001.12
DO  - 10.11648/j.ijmpem.20251001.12
T2  - International Journal of Mineral Processing and Extractive Metallurgy
JF  - International Journal of Mineral Processing and Extractive Metallurgy
JO  - International Journal of Mineral Processing and Extractive Metallurgy
SP  - 27
EP  - 37
PB  - Science Publishing Group
SN  - 2575-1859
UR  - https://doi.org/10.11648/j.ijmpem.20251001.12
AB  - The complex and variable mineralogical compositions of transitional gold ore zones pose significant metallurgical challenges. Using a multi-technique analytical approach that integrates geological, mineralogical, and metallurgical data, this study characterises gold ores from transitional zones within Ghana's Ashanti Belt. XRD, light microscopy, XRF, Raman spectroscopy, sulphur and carbon speciation, preg-robbing index (PRI) tests, and diagnostic leaching studies were performed on six representative samples from three mining companies. The results show that the ores, which are mainly rich in quartz and sericite, have variable sulphide (0.11-0.94%) and organic carbon (0.13-2.11%) contents, which significantly affect the cyanidation performance. Raman spectroscopy revealed different levels of carbon maturity, while optical microscopy verified the presence of pyrite and arsenopyrite. Diagnostic leaching showed highly variable gold deportment: gold was distributed among free-milling phases, sulphides, carbonaceous materials (CM), and residual fines. Samples with higher sulphide and organic carbon contents demonstrated strong preg-robbing behaviour and poor cyanide leach recoveries (34-40%), while those with lower contents achieved recoveries of 75-77%. The study highlights the pronounced intra- and inter-sample variability across the transitional zone ores, underlining the inadequacy of conventional processing approaches. It concludes that a geometallurgical framework anchored in integrated multi-technique characterisation is essential for optimising gold recovery and guiding efficient, domain-specific processing strategies for transitional gold ore deposits.
VL  - 10
IS  - 1
ER  -

Copy | Download