mineral

Gold-bearing Quartz and Pyrite

Auriferous Quartz (SiO2 + Au) with Pyrite (FeS2)

Hardness: 6-7 (Quartz portion), 6 (Pyrite); Color: Rusty orange, yellow-gold, metallic brassy-yellow, and gray; Luster: Vitreous to metallic; Crystal structure: Trigonal/Isometric; Cleavage: None/Indistinct; Specific Gravity: 2.65 - 5.0+

Hardness: 6-7 (Quartz portion), 6 (Pyrite)
Color: Rusty orange, yellow-gold, metallic brassy-yellow, and gray
Luster: Vitreous to metallic

Identified June 25, 2026More mineral →

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Physical properties

Formation & geological history

Hydrothermal vein formation where hot, mineral-rich fluids circulate through fractures in the crust. In Central Kalimantan (Borneo), these are often associated with volcanic arcs and tectonic activity from the Miocene epoch.

Uses & applications

Primary source of gold ore for mining; also collected as mineral specimens representing 'Fool's Gold' and real gold.

Geological facts

The location in Central Kalimantan is part of a major gold-producing belt in Southeast Asia. Pyrite often forms 'pseudomorphs' or weathers into Limonite, giving the rocks their characteristic rusty orange color.

Field identification & locations

Identify in the field by the metallic shine of pyrite against white/gray quartz and heavy iron staining (rust). Found in riverbeds or near mountain outcrops in known mineral belts like the Kalimantan interior.

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Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

Green Apatite on Albite

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mineral