Best Practices for Accurate In Situ Geochemical Analysis

In situ geochemical analysis refers to elemental testing performed directly on geological materials in their natural location, avoiding the delays and costs associated with laboratory testing. While in situ geochemical analysis delivers immediate elemental data, the reliability of those results depends heavily on proper field methodology. Portable analytical technologies used in mining and mineral exploration are powerful, but like any scientific tool, they require disciplined sampling and measurement techniques to produce defensible data.

Understanding why best practices matter begins with recognizing one key principle: the instrument can only analyze what is directly in front of it. If the sample is inconsistent, contaminated, or poorly positioned, the results will reflect those issues.

Below is a deeper look at the technology used for analysis, and the four core best practices that help significantly improve data quality.

Portable XRF Technologies

Handheld X-ray fluorescence (XRF) analyzers facilitate and provide rapid, non-destructive elemental analysis of geological samples.

XRF is an acronym for X-ray fluorescence spectroscopy. XRF is a non-destructive analytical technique used to determine the elemental composition of materials. Handheld XRF analyzers work by measuring the fluorescent (or secondary) X-rays emitted from a sample when excited by a primary X-ray source.

Each of the elements present in a sample produces a set of characteristic fluorescent X-rays, or “unique fingerprints”. These “fingerprints” are distinct for each element, making handheld XRF analysis an excellent tool for quantitative and qualitative measurements.

These portable devices interpret these ‘fingerprints’ and enable immediate, on-site analysis, supporting quick decision-making and more efficient exploration activities. By delivering accurate elemental composition data, portable XRF technology enhances the speed and precision of geological surveys, making it an indispensable tool for prospecting, exploration, and optimizing mining operations.

1. Ensure Samples Are Representative

A representative sample accurately reflects the overall material being evaluated. In geological and environmental contexts, materials are rarely uniform. Elemental concentrations can vary within centimeters due to mineralization patterns, grain size differences, or contamination hotspots.

If a measurement is taken on an unrepresentative surface:

Results may overestimate or underestimate true concentrations
Ore boundaries may be misidentified
Contamination mapping may become inaccurate
Follow-up laboratory assays may not correlate

To improve representativeness:

Remove weathered or altered surface layers when possible
Avoid measuring visibly heterogeneous areas
Take multiple readings across a defined area
Average results when appropriate

Representative sampling reduces variability and increases confidence in field-based elemental analysis. Practically, handheld XRF measurements performed directly on rocks or soils are at best semi-quantitative and provide only ballpark figures in terms concentrations. Those results remain useful to locate pollution hotspots or ore-waste boundaries.

2. Prepare Powdered or Homogenized Materials for Quantitative Analysis

In situ testing can be performed directly on rock faces, soil surfaces, or drill core. However, for quantitative geochemical analysis, sample preparation significantly enhances accuracy.

Why? Because surface texture, particle size, localized heterogeneities and mineralogy can influence X-ray interaction and signal detection.

Grinding and homogenizing a sample:

Reduces particle size effects
Minimizes localized mineral concentration bias
Improves repeatability
Produces more consistent matrix density

Powdered samples provide a more uniform analytical surface, which improves measurement precision and considerably reduces statistical noise. For screening purposes, minimal preparation may suffice. For reporting quantitative concentrations, homogenization is strongly recommended.

3. Use Stable Measurement Setups

Measurement geometry plays a critical role in portable elemental analysis. Inconsistent positioning, movement during analysis, or uneven contact between the analyzer and sample can introduce variability.

Common stability issues include:

Gaps between instrument window and sample
Shifting during measurement
Uneven sample surfaces
Variable angle positioning

Using stable setups — such as flat sample cups, test stands, or firm surface placement — helps ensure consistent X-ray path length and detector exposure.

Stability improves:

Signal consistency
Reproducibility
Detection limits
Overall data reliability

Even small inconsistencies in positioning can affect results, especially when analyzing trace-level elements.

4. Apply Appropriate Calibration Adjustments for Specific Matrices

A “matrix” refers to the overall composition and physical characteristics of a sample. Geochemical samples all have different matrix properties that influence X-ray absorption and enhancement effects.

Without proper calibration:

Elemental concentrations may be biased
Light elements may be under- or over-reported
Results may not correlate with laboratory assays

Modern portable analyzers use often fundamental parameter (FP) models combined with empirical adjustments to compensate for matrix effects. Selecting the correct analytical mode or calibration profile for the sample type is essential.

Moreover, applying type standardization (matrix-specific calibration adjustments) improves:

Accuracy of quantification
Correlation with lab data
Traceability and data defensibility in regulatory or reporting contexts

Calibration is not just a software setting — it is a process that helps ensure the instrument interprets fluorescence signals correctly. We recommend that you monitor drifts and verify accuracy of calibration by running relevant certified reference materials.

Integrating Field Screening and Laboratory Confirmation

In situ geochemical analysis is most powerful when integrated into a broader analytical workflow.

Field screening provides high density of measurement for:

Immediate decision support
Rapid anomaly detection
Real-time drill targeting
Efficient contamination mapping

Laboratory confirmation provides:

High-precision validation
Regulatory-grade reporting
Advanced multi-method analysis

When combined strategically:

Field data reduces unnecessary laboratory submissions
Laboratory data validates and refines field calibration
Overall project timelines shrink
Analytical budgets are optimized

Rather than replacing laboratory analysis, in situ testing enhances it. The two approaches work best as complementary tools within a data-driven field strategy.

Summary

In situ geochemical analysis delivers speed and flexibility. However, accuracy depends on disciplined sampling, preparation, measurement stability, and proper calibration.

Organizations that apply these best practices achieve:

Stronger correlation with laboratory assays
Lower analytical uncertainty
More defensible reporting
Greater operational confidence

In modern field operations, data quality is not determined by the technology alone — it is determined by the accuracy of the analyzer and how the technology is used.

Read more about in situ analysis for mining and minerals in our Application Note: Exploring New Frontiers of In Situ Geochemical Analysis