Native gold and platinum-iron alloy. Kalimantan, Indonesia

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This section is a carbon-coated gold concentrate from a modern placer deposit. Irregular to rounded native gold grains with gold enrichment rims are red-purple to blue-purple respectively. A rounded grain of platinum-iron alloy is brick red (centre). Low-reflectance minerals, mainly zircon and quartz, appear very similar to the mounting material which comprises the bulk of the surface. Black areas arc polishing pits, the rounded ones are erupted air bubbles in the resin. The surface colours depend upon the thickness of the carbon-coat, but the light blue-white colour of the coated resin is characteristic.

Grain mount, plane polarized light, x 22, air

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