Devil is in the detail: how sampling and domaining drive project value

In the development of projects, the journey from concept to construction is often viewed through the lens of engineering design, capital estimates, and feasibility studies.  

Yet, beneath these high-level deliverables lies a critical foundation: the quality and representativeness of metallurgical data. This data – derived from sampling, ore characterisation, and testing – forms the bedrock of process design and ultimately determines the economic viability of a project.

This article explores how attention to detail in sampling and flotation domaining can unlock substantial value in projects. Drawing on two copper case studies undertaken by the authors, it demonstrates how best-practice approaches have led to significant increases in resource size, project scale, and early-year metal production.

The hidden power of sampling

Sampling is often treated as a routine step in project development. However, its impact is anything but routine. Poor sampling practices can lead to misleading metallurgical results, flawed process design, and over or underestimation of project potential. Common pitfalls observed in copper projects include:

• overuse of composite samples that mask variability across ore types
• insufficient and excessive sample mass for reliable flotation and comminution testing
• lack of spatial and lithological coverage, resulting in unrepresentative data.

In contrast, best-practice sampling involves a deliberate strategy to capture the full variability of the orebody. This includes:

• domain-specific sampling across lithologies, mineral assemblages, and geospatial zones
• adequate sample mass to support robust flotation and comminution testing
• integration with geological models to ensure representativity.

Such practices not only improve the reliability of metallurgical predictions but also enable more accurate mine planning and process design.

Domaining: a strategic tool for optimisation

Domaining refers to the segmentation of an orebody into zones based on metallurgical behaviour – particularly flotation and comminution characteristics. When applied rigorously, domaining transforms metallurgical testing from a generic exercise into a strategic tool for optimisation. Sedgman’s experience shows that flotation and comminution based domaining can lead to dramatic improvements in project metrics. It allows for:

• tailored flotation circuit design that matches domain-specific recovery profiles
• improved resource classification, identifying zones previously considered uneconomic
• optimised mine scheduling, prioritising high-recovery zones early in the life of mine.

This is illustrated by the following two case study summaries.

Case study 1: Flotation domaining unlocks resource growth

In this project, initial metallurgical testing based on bulk composite samples suggested limited flotation performance and a constrained resource. However, the project team recognised the limitations of this approach and implemented a domain-based sampling and testing strategy.

Key steps included:

• geospatial mapping of flotation response, using geological and mineralogical data
• targeted sampling across distinct lithological domains
• bench-scale flotation testing to define recovery curves for each domain.

Figure 1 shows flotation data interpretation employing the historical domaining approach with curve of best fit. In contrast, Figure 2 separates analysis of flotation data using the new domaining approach using the three categories (oxide, transition and sulphide). Instead of a curve applied to a composite sample, curves were separately applied to the sulphides. This showed elevated flotation performance at lower grades for this domain versus the historical prediction. 

Figure 1. Flotation data interpretation employing the historical domaining approach with curve of best fit. 

Figure 2. Separate analysis of flotation data using the new domaining approach using the three categories (oxide, transition and sulphide). 

This led to several ore zones previously excluded from the resource model being reclassified as economically viable based on their favourable flotation performance. This led to a 27 per cent increase in the resource and a 29 per cent increase in project scale.

For the study, the flotation circuit was redesigned to accommodate domain-specific recovery strategies, including:

• variable reagent regimes tailored to mineralogy
• selective rougher-cleaner configurations for different domains
• flexible residence time management to optimise recovery.

This domain-driven approach not only improved recovery but also enhanced the robustness of the process design, reducing risk during commissioning and ramp-up.

Case Study 2: Scheduling for performance

A second project highlighted the importance of integrating flotation and comminution sampling with geospatial analysis. In this case it was found that hardness didn’t vary by depth, but instead varied along the length of the proposed pit. Figure 3 below shows the representation of the core hardness variability across the proposed pit shell, with the hardness range for each domain shown in the inset graph.

Figure 3. Representation of the core hardness variability across the proposed pit shell, with the hardness range for each domain shown in the inset graph. 

By understanding how ore characteristics varied across the deposit, the team proposed a new operating schedule that prioritised high-performance domains in the early years.

This strategy involved:

• mapping flotation and comminution performance across the orebody
• aligning mine scheduling with metallurgical performance zones
• deferring lower-recovery material to later stages of the mine life.

The result was a 34 per cent increase in copper production over the first four years of operation. This uplift had a profound impact on project economics, improving cash flow, reducing payback period, and increasing NPV.

Collaboration and multidisciplinary integration

One of the key themes emerging from these case studies is the importance of collaboration. Sampling, domaining, and metallurgical testing are not isolated tasks – they require integration across geology, mine planning, metallurgy, and process engineering. Best-practice project development involves:

• joint planning between geologists and metallurgists to define sampling strategies
• real-time feedback loops between test work results, process design and mine planning
• cross-functional reviews to validate domain definitions and recovery assumptions.

This truly integrated multidisciplinary approach ensures that metallurgical data is not only accurate but also actionable, supporting decisions that enhance project value. Increased yield within the pit will generally mean less water and energy used per metal tonne produced. This increased granularity of domain-based data also allows project teams to model the water, fuel and energy footprint reduction per produced metal tonne from alternate mine plans, and across the life of mine.

Implications for mine managers and executives

For mine managers and executives, the message is clear: sampling, comminution and flotation based domaining are strategic levers for value creation. Since decisions based on this data can have significant impact on financial value, this work should be treated with the same rigour and investment as financial modelling. Key takeaways include:

• invest early in representative sampling programs that reflect orebody variability
• champion domain-based metallurgical testing to inform process design and mine planning
• use comminution and flotation domaining to challenge assumptions, especially in marginal zones
• integrate geospatial analysis to optimise scheduling and early-year performance
• model the energy, fuel and water use per metal tonne produced.

By embedding these practices into project development workflows, mining companies can unlock hidden value, reduce technical risk, and improve project financial and sustainability outcomes.

Conclusion

The devil truly is in the detail. Sampling and flotation domaining may seem like technical minutiae, but they have significant impacts on project success. As demonstrated by these case studies, investment in best-practice approaches can lead to substantial increases in resource size, project scale, and early-year higher value production. In an industry facing increasing pressure to deliver economically and sustainably, these practices offer a pathway to smarter, more resilient project development.

If you are interested to have conversations on these topics, please contact the authors.