Mitigating the Nodule Nugget Effect in Coarse-Gold Drilling Programmes

The Challenge of Heterogeneous Coarse Gold

In high-grade quartz vein gold deposits, gold frequently occurs as discrete, coarse metallic flakes rather than finely disseminated particles. Standard 50g fire assays can either completely miss a gold flake (false negative) or capture one (exaggerated spike), skewing resource estimates.

Screen Fire Assay (SFA) Protocol

To eliminate this nugget bias, RVA Labs offers Screen Fire Assaying on a full 1,000g sample. The entire kilogram is pulverized and screened through a 106 μm (140-mesh) sieve. The coarse fraction (+106 μm) is fire assayed in its entirety, while the fine fraction (-106 μm) is fire assayed in duplicate.

Weighted Grade Calculation

A mathematically weighted average combines coarse and fine values, delivering true, representative gold grades for structurally complex vein systems.