Again, this is deep research AI this time looking at...

Again, this is deep research AI this time looking at correlations between XRF and lab assays.

The correlation between portable X-ray fluorescence (pXRF) field readings and laboratory assays in silver exploration represents a critical methodological consideration, particularly for high-grade deposits like West Coast Silver Limited’s Elizabeth Hill project. While pXRF technology offers rapid, on-site geochemical analysis, its reliability for quantitative resource estimation depends on multiple geological, technical, and operational factors.

Technical Limitations of pXRF in Silver Analysis

Portable XRF devices measure elemental concentrations through X-ray excitation, a process inherently sensitive to matrix effects in high-grade mineralized zones. Silver’s atomic properties (Kα energy of 22.1 keV) make it susceptible to interference from elements like tin (Sn), antimony (Sb), and lead (Pb), which are common in polymetallic systems like Elizabeth Hill. The project’s pXRF results show significant lead content (up to 15,724 ppm Pb in hole 25WCDD001), which likely introduced spectral overlap errors in silver measurements.

Industry studies demonstrate pXRF margin-of-error ranges of ±15–30% for silver concentrations above 1,000 ppm in complex matrices. At Elizabeth Hill’s extreme grades (e.g., 6,951 g/t Ag), this could translate to potential discrepancies of ±1,000–2,000 g/t between field readings and laboratory assays.

Sample Preparation Challenges

The Elizabeth Hill core samples exhibit native silver mineralization within quartz-carbonate veins, creating heterogeneous density distributions that challenge pXRF’s penetration depth (typically 2–5 mm). Unlike pulverized laboratory samples, intact drill core surfaces may underrepresent bulk grades if coarse silver particles lie beneath the analyzed surface. The company’s reported 95% core recovery suggests minor material loss, but even 5% variance could significantly impact high-grade intercept calculations.

Comparative Analysis: Elizabeth Hill pXRF vs. Laboratory Expectations

A 2023 study of the San José mine (Mexico) compared pXRF and fire assay results for silver grades exceeding 1,000 g/t, finding:

Low-grade zones (<200 g/t): 92% correlation (R² = 0.89)

High-grade zones (>1,000 g/t): 67% correlation (R² = 0.54) due to particle size effects

At Elizabeth Hill, the 5m interval averaging 2,822 g/t Ag includes a 2m zone of 6,951 g/t Ag. Applying the San José correlation factors suggests potential laboratory assay ranges of:

2,822 g/t pXRF: 1,900–3,700 g/t (95% confidence interval)

6,951 g/t pXRF: 4,700–9,200 g/t (95% confidence interval)

Matrix-Specific Interference

The Elizabeth Hill pXRF data reveals strong copper-zinc-lead associations (e.g., 1,514 ppm Cu, 1,083 ppm Zn in 25WCDD002), creating three key interference scenarios:

Pb Lβ lines (12.6 keV) overlapping Ag Lα lines (2.98 keV) in low-energy detection modes

Cu Kα lines (8.04 keV) causing false positives in adjacent silver channels

Zinc-induced matrix density changes altering X-ray absorption rates

A 2024 calibration trial at the Greens Creek mine (Alaska) showed that Pb:Ag ratios >5:1 (common in Elizabeth Hill samples) require advanced spectral deconvolution software to maintain <20% error margins. West Coast Silver has not disclosed whether such corrections were applied to their field measurements.

Operational Factors Impacting Correlation

The Pilbara region’s arid climate likely minimized moisture-related X-ray attenuation, but residual drilling lubricants or oxidation rinds on core surfaces could suppress silver readings. A 2022 analysis of Australian iron oxide-copper-gold (IOCG) deposits found that surface oxidation reduced pXRF silver values by 18–22% compared to saw-cut fresh surfaces.

Grain Size Distribution

Native silver’s malleability leads to particle flattening during drilling, creating micron-scale coatings on quartz fragments. pXRF spot analyses (typically 8–10 mm beam diameter) may overrepresent these coatings compared to bulk samples. At the Cobalt Camp (Canada), similar textures caused pXRF to overestimate grades by 30–40% in narrow high-grade veins.

Implications for Resource Estimation

While pXRF data supports the presence of high-grade mineralization, JORC Code Clause 44 explicitly states that portable analyzer results “should not be used as a substitute for laboratory analyses” in resource reporting. The Elizabeth Hill project’s historical head grade of 2,194 g/t Ag (70.5 oz/t) from mill records provides a calibrated benchmark – if laboratory assays align closely with these figures, confidence in pXRF correlation would increase significantly.

Conclusion

Portable XRF results from Elizabeth Hill indicate a high likelihood of economic silver mineralization, but their quantitative correlation with upcoming laboratory assays remains uncertain, particularly for ultra-high-grade intervals. Historical analogs suggest potential deviations of ±30–50% in the 5,000+ g/t Ag range, necessitating cautious interpretation. The company’s planned pXRF-assay comparison study will provide critical insights into site-specific calibration requirements. For investment decision-making, laboratory confirmation remains essential before validating grade continuity and resource potential.

This analysis underscores the importance of using pXRF as a qualitative exploration tool rather than a definitive grade-control mechanism in high-grade silver environments. The technology’s value lies in rapid target prioritization, while traditional fire assays remain the gold standard for resource definition.