Introduction: The role of sample preparation in mineral analysis

Mining laboratories turn raw geological material into reliable analytical data that supports exploration, resource evaluation, and process optimization. Reliable mineral analysis depends not only on the analytical instrument, but also on how well samples are prepared, homogenized, and separated before they reach XRF, AAS, or ICP-MS/ICP-OES systems.  
 
At every stage of the workflow, from ore sampling to final reporting, laboratories must control variables that can introduce bias or error. Consistent sample preparation is essential for maintaining data quality and traceability across batches, deposits, and sites. OHAUS supports these workflows with practical laboratory instruments for heating, mixing, and separation in demanding mining environments. 
 

* XRF - X‑ray Fluorescence 
   AAS - Atomic Absorption Spectroscopy 
   ICP - Inductively Coupled Plasma 

Mining laboratory workflow: from sampling to instrumental analysis

1.Field and core sampling

In mining operations, analytical quality begins in the field. Ore and rock samples are collected from exposed faces, drill cores, or production streams according to defined sampling procedures so that the material is representative of the deposit or process stream. Once samples arrive in the laboratory, the focus shifts to controlled and repeatable preparation.

2. Comminution and preliminary homogenization 

Bulk samples are typically crushed, milled, and sieved to obtain a suitable grain size for laboratory analysis. The goal is to reduce heterogeneity and prepare material that can be subsampled reliably for digestion or fusion. If non-uniformity remains at this stage, it will directly affect the analytical result. 

3. Wet sample preparation and digestion 

For many elemental analysis methods used in mining, such as ICP-OES, ICP-MS*, and AAS, solid samples must be converted into clear solutions. This usually involves acid digestion, fusion followed by dissolution, or other chemical treatment designed to break down the mineral matrix and release analytes of interest. 
 
OHAUS hotplates and dry block heaters support controlled digestion and heating steps in mining laboratories. Guardian 5000 and Guardian 7000 hotplate stirrers combine precise heating and mixing for demanding sample preparation workflows, while stir-only models in the Guardian 2000 and Guardian 5000 ranges can support mixing during pH adjustment and similar wet chemistry steps. Consistent heating helps drive digestion reactions to completion and reduces the risk of biased downstream results.  

[Guardian 5000] 
[Guardian 7000] 
[Dry Block Heaters] 

*ICP-OES – Inductively Coupled Plasma Optical Emission Spectrometry 
  ICP-MS – Inductively Coupled Plasma Mass Spectrometry 

Mixing and homogenization: ensuring representative test portions  

4. Slurry preparation and solution homogenization 

After digestion or dissolution, samples must be thoroughly mixed to ensure homogeneity before any aliquot is transferred for analysis. In mining laboratories, this often means handling dense slurries, viscous suspensions, or solutions containing fine particulate residues. 
 
OHAUS Achiever 5000 Overhead Stirrers, Open Air Shakers, and vortex mixers provide flexible support for these tasks. Achiever 5000 overhead stirrers are designed for reliable mixing of viscous liquids and mineral slurries, with precise digital speed control and high torque. Open Air Shakers offer multiple motion types and capacities suited to continuous agitation, while Heavy Duty Open Air Shakers are particularly relevant for higher-throughput preparation. Vortex mixers support quick resuspension of small sample volumes at the bench.  

[Achiever 5000 Overhead Stirrers] 
[Heavy Duty Open Air Shakers] 
[Vortex Mixers] 
 
Consistent homogenization is critical at this stage. If the sample is not fully homogeneous, subsampling for XRF, MS, or AAS can lead to significant variability in measured elemental concentrations, even when analytical instruments themselves are stable and well calibrated.

Centrifugation and separation: preparing clean solutions  

5. Solid-liquid separation after digestion 

Many mineral digestion protocols produce suspensions that contain both dissolved analytes and undissolved residues. Before analysis, laboratories often need to separate these phases to protect instruments, improve sample clarity, and reduce matrix effects. Filtration and centrifugation are common approaches. 
 
OHAUS Frontier centrifuges provide efficient and controlled solid-liquid separation within these workflows. Available in micro, universal, and high-capacity formats, they offer controlled speeds and run times, compatibility with multiple tube formats, and safety features such as active imbalance detection. Reliable centrifugation helps improve sample clarity before instrumental analysis, reduce blockages and contamination, and support more stable MS, OES and AAS measurements. 
 
[Frontier Centrifuges] 
[Frontier Accessories] 
 

Instrumental analysis: XRF, AAS, and MS 

6. Elemental analysis of ores and concentrates 

Once samples are digested, homogenized, and clarified, they are ready for instrumental analysis. Mining laboratories rely heavily on XRF, AAS, and MS-based techniques to quantify major, minor, and trace elements in ores, concentrates, tailings, and process solutions.  
 
The quality of these results depends strongly on how well the upstream preparation steps have been controlled. Any variability introduced during digestion, mixing, or separation will directly affect precision, comparability, and confidence in the analytical data. 

Mining sample preparation workflow and OHAUS equipment 

 

Workflow step	Main objective	Typical analytical  techniques	Relevant OHAUS  equipment
Field and core  sampling	Obtain representative primary samples	All downstream techniques	Not applicable (field operation)
Comminution and  preliminary homogenization	Reduce particle size and improve homogeneity	XRF, ICP, AAS	Not applicable (crushers and mills are non-OHAUS)
Wet sample preparation and digestion	Dissolve the mineral matrix and release analytes	ICP, AAS, sometimes XRF solutions	Guardian 5000 / Guardian 7000 Hotplate Stirrers, Dry Block Heaters
Slurry preparation  and homogenization	Maintain suspension and ensure homogeneity	XRF slurries, ICP, AAS	Achiever 5000 Overhead Stirrers, Open Air Shakers, Vortex Mixers
Solid-liquid  separation	Clarify solutions and protect instruments	ICP, AAS	Frontier Centrifuges
Instrumental analysis	Quantify elemental composition	XRF, ICP-OES, ICP-MS, AAS	Not applicable (separate analyzers)

Why workflow consistency matters in mining laboratories

Pre-analytical stages often contribute a substantial share of total analytical error. Uneven heating, incomplete digestion, insufficient mixing, or inconsistent separation can distort the apparent composition of ores and concentrates.  
 
By standardizing equipment and procedures, laboratories can reduce pre-analytical variability and improve repeatability over time. Robust heating, mixing, and separation equipment also makes it easier to support SOP compliance, document parameters, and reproduce conditions across batches and sites. 

OHAUS laboratory equipment in mining sample preparation  

OHAUS offers a range of laboratory equipment that fits naturally into the mining sample preparation workflow: 
 

• Guardian 5000 and Guardian 7000 Hotplate Stirrers for controlled, reproducible heating and stirring during digestion and reagent preparation.  

• Achiever 5000 Overhead Stirrers for intensive mixing of mineral slurries and viscous suspensions. 

• Open Air Shakers and Vortex Mixers for consistent agitation and homogenization in a variety of vessel formats, including higher-throughput applications. 

• Frontier Centrifuges for fast and reliable solid-liquid separation after digestion.  

 
This equipment helps mining laboratories build robust and repeatable workflows that support high-quality data and efficient operation.

Conclusion: Reliable preparation for confident mineral analysis 

Accurate mineral analysis supports decisions from exploration drilling to process control and long-term planning. While advanced instruments produce the final measurement, result quality still depends on the consistency of upstream sample preparation. 
By using dependable laboratory equipment for heating, mixing, and separation, mining laboratories can improve reproducibility, reduce preparation errors, and strengthen data integrity. OHAUS supports these goals with equipment designed for consistent performance in demanding mining environments. 

FAQ: Mining laboratory equipment and mineral analysis workflows

Why is mining sample preparation equipment so important for XRF and ICP-MS/OES? 

Because it controls particle size, homogeneity, and matrix conditions before measurement; poor preparation can lead to variable or biased XRF, ICP-MS/OES, and AAS results. 

What are the critical steps in mineral sample preparation? 

The main steps are sampling, comminution, homogenization, digestion or fusion, and solid-liquid separation before analysis. 

Which OHAUS products are most relevant for mining laboratories? 

Guardian 5000/7000 Hotplate Stirrers, Achiever 5000 Overhead Stirrers, Heavy Duty Open Air Shakers, and Frontier centrifuges support the key stages of sample preparation before XRF, AAS, and ICP analysis. 

How does consistent mixing affect mineral analysis results? 

It helps keep each aliquot representative, improving repeatability and reducing reruns.

Can OHAUS mining laboratory equipment be integrated into automated workflows? 

Yes. OHAUS equipment can be combined with external sample handling and data systems to support more standardized and documented workflows.