When assay results show variability, analytical instrumentation is often assumed to be the cause. In practice, however, the source of error is more frequently introduced during sample preparation.
Sample preparation is where data integrity is either established or compromised.
Common points of error introduction:
– Crushing and Pulverising: Loss of fine fractions or selective loss of minerals of interest
– Splitting: Particle size or density segregation leading to non-representative splits
– Sub-sampling: Inadequate representativeness, particularly in heterogeneous matrices
In nuggety gold systems, minor preparation errors can materially distort grade distribution and influence downstream technical and economic decisions.
Practices adopted by high-performing laboratories:
Sample preparation is managed as a controlled process rather than a routine operation.
✔ Documented cleaning and decontamination procedures between samples
✔ Verification of particle size specifications at each comminution stage
✔ Systematic insertion of field duplicates, blanks, and certified reference materials to monitor preparation precision and detect contamination
In exploration and resource evaluation, data quality is determined before instrumental analysis.
Preparation defines representation. Representation defines reality.
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