Rock Identifier
Gold-bearing Quartz with Pyrite (Quartz (SiO2) with Gold (Au) and Pyrite (FeS2)) — mineral
mineral

Gold-bearing Quartz with Pyrite

Quartz (SiO2) with Gold (Au) and Pyrite (FeS2)

Hardness: 7 (Quartz) to 2.5 (Gold); Color: Milky white to grey quartz with metallic brassy yellow/gold flecks; Luster: Vitreous (Quartz) to Metallic (Pyrite/Gold); Crystal structure: Trigonal (Quartz), Cubic (Pyrite); Specific Gravity: 2.65 (Quartz) vs 19.3 (Gold).

Hardness
7 (Quartz) to 2
Luster
Vitreous (Quartz) to Metallic (Pyrite/Gold)
Identified More mineral

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Physical properties

Hardness: 7 (Quartz) to 2.5 (Gold); Color: Milky white to grey quartz with metallic brassy yellow/gold flecks; Luster: Vitreous (Quartz) to Metallic (Pyrite/Gold); Crystal structure: Trigonal (Quartz), Cubic (Pyrite); Specific Gravity: 2.65 (Quartz) vs 19.3 (Gold).

Formation & geological history

Formed in hydrothermal veins where hot, mineral-rich fluids circulate through fractures in the Earth's crust. Often associated with orogenic belts and tectonic activity, ranging from Precambrian to Cenozoic ages.

Uses & applications

Primary source of elemental gold for bullion, electronics, and jewelry. Specimens are highly valued by mineral collectors and as 'ore' samples for geological study.

Geological facts

Most 'gold' seen in quartz is often 'Fool's Gold' (Pyrite), but genuine gold is often found alongside it in small wires, grains, or flakes. The California Gold Rush was driven by the discovery of such quartz veins.

Field identification & locations

Identify in the field by checking for high metallic luster that doesn't tarnish when wet. Genuine gold is malleable (will dent, not shatter), whereas pyrite is brittle. Commonly found in riverbeds (placer deposits) or near old mining shafts in mountainous regions.