Gold-platinum placer. Kalimantan, Indonesia

The samples are a gold-rich concentrate from a river placer.

Major Minerals:

Gold-silver alloys, zircon, ilmenite, magnetite, cassiterite, pyrite

Minor and trace Minerals:

Include platinum-iron alloys, iridosmine, osmiridium, chromite, cinnabar, marcasite, rutile.


The gold fineness is related to its colour and reflectance. Gold enrichment rims have lower reflectance and are deeper yellow than the silver-rich cores. Copper-bearing gold-silver alloys are pinker than gold-silver alloys


Stumpfl and Clark, 1965; Stumpfl, 1974; Bowles et al., 1984