Geologists often face significant challenges when it comes to the recovery of gold from refractory ores. These ores, which contain gold particles locked within sulphide minerals or organic carbon, typically yield lower recovery rates using traditional methods like cyanidation. While existing technologies such as roasting, bio leaching, and pressure oxidation have improved recovery rates to around 80-90%, they may still overlook a substantial amount of gold – encapsulated nanogold(TM) – that could be extracted using more advanced techniques like that offered by IPRI.Tech: chemical free ultra-high pyro-metallurgical process called PAD(TM).
Understanding Refractory Ores
Characteristics of Refractory Ores
Refractory gold ores are resistant to conventional recovery methods due to:
Physical Encapsulation: Gold particles are often less than a few micrometers in size and are trapped within nonreactive minerals, making them impervious to leaching processes[1][2].
Chemical Interference: Certain constituents in the ore can inhibit the effectiveness of cyanide leaching, further complicating recovery efforts[2][4].
According to estimates, approximately 24% of gold reserves are classified as refractory, necessitating sophisticated treatment methods[1][7]. The common pre-treatment options include ultra-fine grinding, bio-oxidation, roasting, and pressure oxidation. Each of these methods aims to liberate the encapsulated gold or remove carbonaceous materials that can adsorb dissolved gold during leaching.
Limitations of Current Recovery Techniques
Despite advancements in recovery technologies, geologists may not fully realise the potential for higher gold recoveries due to several factors:
Underestimation of Gold Content: Traditional assays may not account for fine or nanogold that could be liberated through more aggressive processing techniques like PAD(TM).
Scepticism Towards New Technologies: Many geologists are cautious about adopting new methods due to a lack of familiarity and proven success rates compared to established practices.
The Case for PAD(TM) Technology
Advantages of PAD(TM)
Chemical free ultra-high pyro-metallurgical technology like PAD(TM) presents a promising alternative for recovering gold from refractory ores. This method can potentially unlock even the most finely dispersed or encapsulated gold particles that traditional methods might miss. Key benefits include:
Higher Recovery Rates: PAD(TM) can achieve recoveries that approach 100 grams per tonne by accessing previously unrecoverable gold[1].
Efficiency in Processing: The technology may reduce the need for multiple pre-treatment steps, streamlining the overall recovery process and potentially lowering operational costs.
Convincing Geologists
To persuade sceptical geologists about the efficacy of PAD(TM) technology, we consider the following strategies:
1. Data-Driven Evidence: Presenting case studies and pilot project results demonstrating successful implementations of PAD(TM) with high recovery rates compared to traditional methods.
2. Collaborative Research Initiatives: Encourage partnerships between mining companies and research institutions to conduct controlled trials that validate the effectiveness of PAD(TM).
3. Cost-Benefit Analysis: Provide a thorough analysis showing how improved recovery rates can offset initial investments in new technology, leading to greater overall profitability.
While current technologies have made strides in recovering gold from refractory ores, there remains significant untapped potential. By leveraging innovative methods like PAD(TM), the mining industry could substantially increase recoverable gold quantities and enhance economic viability.
Further Details of PAD(TM)
PAD(TM) technology is emerging as a transformative method for recovering invisible gold from refractory ores, which traditional extraction methods often fail to effectively process. This technology utilises extremely high temperatures to target and liberate precious metals that are otherwise locked within complex mineral structures.
Mechanism of PAD(TM) Technology
Ultra High Temperature Chemical Free Processing
The PAD(TM) process is chemical free and operates at temperatures ranging from 6,400°C to 14,000°C, significantly exceeding the capabilities of conventional metallurgical techniques. This extreme heat alters the chemical and physical properties of the target material (ore or tailings). The key steps involved include:
1. Ore Injection: The target material is injected into PAD(TM).
2. Heat Cracking: The intense heat cracks the ore structure, breaking down complex minerals that encapsulate precious metals.
3. Cooling: As the material cools, it forms a fine powder containing liberated precious metals, including gold.
This process effectively disintegrates the physical barriers that prevent the recovery of encapsulated gold, allowing for almost complete extraction of latent precious metals[9][10].
Targeting Invisible Gold – “Nanogold(tm)”
Unlocking Encapsulated Metals
Invisible gold often exists in extremely fine particles or is chemically bound within sulphide minerals such as pyrite and arsenopyrite. Traditional methods struggle to recover these forms due to their small size and the protective nature of surrounding minerals. PAD(TM) addresses this challenge through:
Thermal Decomposition: The high temperatures break down sulfide minerals, releasing gold that was previously trapped within their structures[11].
Enhanced Solubility: During the PAD(TM) treatment, gold becomes more soluble in metal sulphides compared to metal silicates, allowing for more efficient collection[12].
Minimal Prill Entrapment: The low viscosity of the molten slag produced during processing reduces the likelihood of gold particles being trapped, ensuring higher recovery rates[11].
Proven Results
Assays conducted by our scientists have demonstrated remarkable increases in gold yields when using PAD(TM) compared to conventional methods. For instance, one assay indicated a jump from 34 grams of gold per metric ton to 500 grams after applying PAD(TM) technology—an increase of over 1,500%[10]. Such results highlight the technology’s potential to uncover significant amounts of previously invisible gold.
Overcoming Scepticism
Despite its promise, geologists may remain sceptical about adopting PAD(TM) technology due to:
Familiarity with Established Methods: Many professionals are accustomed to traditional extraction techniques and may be hesitant to embrace new technologies without extensive validation.
Concerns About Economic Viability: Initial investments in PAD(TM) facilities can be substantial, leading some to question whether the returns justify the costs.
To address these concerns, it is crucial that we at IPRI.Tech present comprehensive data demonstrating successful applications of PAD(TM) in various mining contexts. Collaborating with independent laboratories for third-party validation has also helped build our credibility and trust in this innovative approach.
In summary, PAD(TM) technology represents a significant advancement in the recovery of nanogold from refractory ores. By leveraging high temperatures to liberate encapsulated precious metals, this method not only enhances recovery rates but also opens up new opportunities for mining operations dealing with complex ores.
Analytical Methods for Mineral Content Determination
Here is a comprehensive list of methods used to analyse minerals for their content, along with their limitations in detecting invisible high-value metals such as gold and PGEs.
1. Fire Assay
Description: A traditional method for determining gold and PGEs by melting the sample with fluxes to separate precious metals into a lead button.
Limitations: Ineffective for detecting invisible gold that exists as sub-microscopic particles or chemically bonded within sulphide minerals. Nanogold may remain encapsulated and unaccounted for.
2. Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
Description: Measures trace elements with high sensitivity after dissolving the sample in acid.
Limitations: Cannot detect gold or PGEs if they are not liberated during sample preparation. Encapsulated or chemically bonded metals remain undetected.
3. X-ray Diffraction (XRD)
Description: Identifies crystalline mineral phases by analyzing X-ray diffraction patterns.
Limitations: Cannot detect amorphous or sub-microscopic particles of gold and PGEs. It is also ineffective for distinguishing metals embedded in complex matrices.
4. Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDX)
Description: Provides micro-scale imaging and elemental analysis of mineral surfaces.
Limitations: Limited to surface-level analysis, meaning deeply encapsulated or extremely fine particles of gold and PGEs may go undetected.
5. Gravimetric Analysis
Description: Measures the weight of precipitated compounds to determine metal content.
Limitations: Not suitable for trace or sub-microscopic metals, as it requires larger quantities of the target metal for accurate measurement.
6. Proton Induced X-ray Emission (PIXE)
Description: Uses a proton beam to induce X-ray emission from elements in the sample, allowing for elemental analysis.
Limitations: While PIXE can detect trace elements, it struggles with sub-microscopic or chemically bound forms of gold and PGEs that do not emit distinct signals due to their encapsulation within other minerals[15].
7. NanoSIMS (Secondary Ion Mass Spectrometry)
Description: Provides high-resolution imaging and isotopic analysis at the nanoscale.
Limitations: NanoSIMS can detect invisible gold but is restricted to very small areas, making it impractical for bulk ore analysis[10]. Only personnel skilled in identifying nanogold and nanoPGEs can accurately employ NanoSIMS
8. QEMSCAN (Quantitative Evaluation of Minerals by Scanning Electron Microscopy)
Description: Combines SEM imaging with automated mineralogical analysis to map mineral associations.
Limitations: QEMSCAN may misidentify or overlook sub-microscopic particles of gold due to its reliance on surface-level imaging[15].
Why Nanogold and NanoPGEs are Often Missed
Invisible high-value metals like gold and PGEs are challenging to detect due to the following reasons:
1. Physical Encapsulation
Invisible gold often exists as nanometre-scale particles trapped within sulphide minerals like pyrite or arsenopyrite. Analytical methods that rely on bulk dissolution or surface imaging fail to access these encapsulated particles[2][7].
2. Chemical Bonding
Gold can form solid solutions within the lattice structures of host minerals or chemically bond with other elements like arsenic. These forms are undetectable by most traditional assays unless the host mineral is completely broken down[2][7].
3. Detection Limits
Many techniques have detection thresholds that cannot account for trace amounts of metals dispersed at sub-microscopic levels.
4. Mineral Complexity
In complex ores, precious metals are often associated with multiple phases, making it difficult to isolate and analyse them accurately using conventional methods.
5. Sample Preparation Issues
Improper sample preparation can leave encapsulated metals intact, leading to underestimation of their presence.
While existing analytical techniques provide valuable insights into mineral content, they often fail to detect nano particle size high-value metals like gold and PGEs due to encapsulation, chemical bonding, and detection limitations. Advanced extraction methods like PAD(TM) technology offer a solution by liberating these hidden metals through extreme heat processes, making them accessible for recovery.
High Concentrations of Nanogold
1. Nanoparticle Formation and Transport
Recent studies have shown that gold can exist as nanoparticles, typically ranging from 1 to 10 nanometers in size. These nanoparticles can form in various geological environments, particularly in hydrothermal fluids where conditions allow for the stabilisation of colloidal gold. For instance, research indicates that gold concentrations in some ore-forming fluids can reach exceptional levels, with reports of up to 750 ppm (parts per million) in fluid inclusions, and even higher concentrations in specific geological settings[22][24].
2. Aggregation Mechanisms
Gold nanoparticles can aggregate and coalesce under certain conditions, leading to the formation of larger particles or clusters. This aggregation can significantly increase the total amount of recoverable gold within a given volume of ore. In some cases, these processes can lead to “bonanza-type” ore zones where high-grade concentrations of gold are found due to the accumulation of these nanoparticles[23][25].
3. Geological Conditions Favoring Nanogold
The geological conditions under which orogenic gold deposits form—such as low salinity and high pressure—are conducive to the stable migration and precipitation of colloidal gold. Under these conditions, gold can be transported over considerable distances within hydrothermal fluids before being deposited as nanoparticles when physicochemical conditions change[24][25]. This mechanism allows for significant amounts of gold to be present in forms that are not easily detectable by conventional assays.
Why Geologists May Not Detect This Gold
1. Limitations of Conventional Assays
Traditional methods such as fire assays and ICP-MS often focus on larger, visible gold particles and may not effectively capture the presence of nanogold. These techniques typically require complete dissolution or visible manifestation, which invisible or fine particles may not provide.
2. Assumptions Based on Historical Data
Geologists often rely on historical data and established models that may not account for the presence of nanogold or its potential concentrations. If previous assessments were based on visible gold alone, it is understandable that they might underestimate the total content.
3. Complex Mineral Associations
Invisible gold is frequently found within complex mineral matrices, making it difficult to isolate during sample preparation and analysis. This complexity can lead to significant under reporting if the analytical techniques do not adequately address the unique characteristics of the ore.
Conclusion
The potential for a geologist to discover typically 10 times additional gold per tonne due to the presence of nanogold(TM) is grounded in current scientific understanding of how gold behaves in geological settings. The aggregation and transport mechanisms that allow for high concentrations of nanoparticles mean that substantial amounts of previously unaccounted-for gold may exist within refractory ores. As such, geologists should consider adopting advanced analytical techniques capable of detecting these invisible forms of gold without any implication of oversight or error on their part.
PAD(TM) can recover these nano-metals for you.
References
1. Getting a Handle on Refractory Ore May Determine Gold’s Near Future – The Assay – https://www.theassay.com/articles/analysis/getting-a-handle-on-refractory-ore-may-determine-golds-near-future/
2. Recovering Refractory Resources – SGS – https://www.sgs.com/-/media/sgscorp/documents/corporate/brochures/sgs-min-2012-04-recovering-refractory-resources-en-13-09.cdn.en-CA.pdf
3. Critical Minerals Are a Gold Rush the West Lost Sight Of – CleanTechnica – https://cleantechnica.com/2025/01/09/critical-minerals-are-a-gold-rush-the-west-lost-sight-of/
4. Gold Recovery from Refractory Ores – Journal of Materials Processing Technology – https://www.journalssystem.com/ppmp/pdf-94852-36015?filename=Gold+recovery+from.pdf
5. US5071477A – Method for recovering gold from refractory ores – Google Patents – https://patents.google.com/patent/US5071477A/en
6. Basics in Mineral Processing Handbook – Metso – https://www.metso.com/globalassets/insights/ebooks/mo-basics-in-mineral-processing-handbook_lowres.pdf
7. Refractory Gold Ores: Challenges and Opportunities for a Key Source of Growth – McKinsey & Company – https://www.mckinsey.com/industries/metals-and-mining/our-insights/refractory-gold-ores-challenges-and-opportunities-for-a-key-source-of-growth
8. Gold Recovery from Refractory Ores: A Review – MDPI – https://www.mdpi.com/2075-163X/9/7/406
9. TOSS Plasma Technologies Limited – SlideServe – https://www.slideserve.com/neil/toss-plasma-technologies-limited
10. Plasma Power: Increasing Precious Metal Yields from Complex Ores – Mining Technology – https://www.mining-technology.com/features/featureplasma-power-increasing-precious-metal-yields-from-complex-ores-4207658/
11. US4891060A – Method for recovering gold from refractory ores – Google Patents – https://patents.google.com/patent/US4891060A/en
12. WO2010058188A1 – Method for recovering gold from refractory ores – Google Patents – https://patents.google.com/patent/WO2010058188A1/en
13. The Use of QEMSCAN and PIXIE in the Characterisation of Complex Gold Ores – Nature Scientific Reports – https://www.nature.com/articles/s41598-023-30219-5
14. Thesis: Doctor of Philosophy Ryan Azadi 2022 – University of Western Australia Repository – https://api.research-repository.uwa.edu.au/ws/portalfiles/portal/197061510/THESIS_DOCTOR_OF_PHILOSOPHY_AZADI_Ryan_2022.pdf
15. Thesis: Final Thesis on Gold Recovery Techniques – University of Queensland Espace – https://espace.library.uq.edu.au/view/UQ:7ba3b46/s4341543_final_thesis.pdf
16. Gold Recovery from Refractory Ores: A Review – MDPI – https://www.mdpi.com/2075-163X/9/7/447
18. IAEA Technical Document TE 1190 – International Atomic Energy Agency (IAEA) Publications – https://www-pub.iaea.org/MTCD/Publications/PDF/te_1190_prn.pdf
19. IAEA Technical Document TE 1342 – International Atomic Energy Agency (IAEA) Publications – https://www-pub.iaea.org/MTCD/Publications/PDF/te_1342_web.pdf
20. The Use of QEMSCAN and PIXIE in the Characterisation of Complex Gold Ores – ResearchGate – https://www.researchgate.net/publication/276319556_The_Use_of_QEMSCAN_and_PIXIE_in_the_Characterisation_of_Complex_Gold_Ores
21. PI and Small Gold Discussion Thread – Detector Prospector Forum – https://www.detectorprospector.com/topic/230-pi-and-small-gold/
22. Understanding How Gold is Concentrated in Ore – Micro – https://micro.org.au/news/understanding-how-gold-is-concentrated-in-ore/
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25. The Role of Bioleaching in the Recovery of Gold from Refractory Ores – MDPI – https://www.mdpi.com/2075-163X/7/9/163
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