Efficiency of cyanidation in gold exploration using soils

Cyanidation allows gold to be extracted from larger samples than is practical by fire assay and may thus provide both a simpler analytical procedure and better sample representativity. Here we compare recovery of gold by cyanidation and fire assay for the -212 +106 mu m and -106 +53 mu m light mineral fractions and the -53 mu m fraction of C-horizon soils from a variety of gold deposits and weathering regimes in Canada and the U.S. Results for cyanidation and fire assay are strongly correlated and for many samples, gold recovery by cyanidation is within +/-20% of values reported by FA-AAS. Somewhat unexpectedly, there is good recovery of gold from unground light mineral fractions in which the gold is encapsulated rather than being present as free gold. Abundance and size distribution of the gold should be considered when deciding if cyanidation offers any real advantage over fire assay-based methods. (C) 1999 Elsevier Science B.V. All rights reserved.