Page 32 - Handbook of Gold Exploration and Evaluation

Table 1.6 Morphology and size of gold vs. source (derived from Fedchuk et al., 1978)

Source of gold Type of gold Morphology of colours Size mm Remarks
Gold from Hypogene Xenomorphic angular, equant elongate, and 0.1±200 Coarse grains
bedrock (primary ores) laminar segregations. rare.
source Hypidiomorphic crystallites glistening facets
and dendritic intergrowths.
Supergene Lumpy, spongy, with pimply pitted surface. 0.1±1000 Fine grains
(zones of Excrescences and projections of irregular shapes, up to 2000 retained.
oxidation) octahedral crystallites and their intergrowths. and more
Placer gold Of hypogene Flaky, drop-like, laminar wire-like, sometimes 250±1000 Fine grains
origin small crystallites with glistening or shagreen dominant dispersed or
surface. Frequent impressions or crystals of agglomerated.
hypogene minerals.
Oxidation Equant, thickly laminate with relicts of lumpy 200±500
zones or spongy structure rarely incomplete dominant up to
crystalline shape; surface pimply pitted 2000±3000
shagreen lustre uneven. rarely nuggets

Hydrogenic Dendrites, `corals', aggregates and intergrowth Precipitation of
of grains drop-like sinters with uneven lustre fines from above.
and rough surface.