Morphology and geochemistry of gold grains in lateritic profiles of southern Mali

PALLADIUM AND PLATINUM MINERALS FROM THE SERRA PELADA Au-Pd-Pt DEPOSIT, CARAJAS MINERAL PROVINCE, NORTHERN BRAZIL

“…The weathering of gold particles under lateritic conditions leads to the development of an Au-rich, Ag-depleted halo (e.g., Mann 1984, Colin & Vieillard 1991, Freyssinet et al 1989, Minko et al 1992, Colin et al 1997, and ultimately, to the formation of grains of com-positionally pure, supergene gold (e.g., Boyle 1979, Mann 1984, Oliveira & Campos 1991, Santosh & Omana 1991, Lawrance & Griffin 1994. Like silver, palladium also is leached from gold alloy during weathering (Varajão et al 2000).…”

Highly pure placer gold formation in the Nilambur Valley, Wynad Gold Field, southern India

“…The mechanisms of liberation of gold from primary deposits, chemical migration in low temperature fluids and redeposition in the weathering profiles have received renewed attention in recent years in light of the potential of such processes to generate economically significant concentrations of gold in laterites (e.g., Mann 1984;Webster and Mann 1984;Wilson 1984;Freyssinet et al 1989;Santosh and Omana 1991). Experimental studies indicate that there is a marked contrast in the solubilities of Ag and Au in acid chloride solutions, such that Ag> > Au (cf.…”

Crystal features of supergene gold at Hannan South, Western Australia

“…However, as their internal crystallographic structure remains the same, the external morphological distinction between plane-faced and rounded crystals does not justify their treatment as distinct genetic varieties as proposed by some workers (e.g. Freyssinet et al 1987Freyssinet et al , 1989. As crystals of different varieties have different internal structures and different growth forms, the effect of dissolution is to bring out these features as sculptures on the faces or to determine the morphology of their partial dissolution forms.…”

“…In the absence of crystal shapes, some authors have approached the description of gold varieties by classifying differing shaped products of dissolution without considering crystallinity (e.g. Freyssinet et al 1989).…”