mineral

Pyrite in Quartz

Iron Sulfide (FeS2) in Silicon Dioxide (SiO2)

Hardness: 6-6.5 (Pyrite), 7 (Quartz); Color: Brass-yellow metallic pyrite in white/translucent milky quartz; Luster: Metallic for pyrite, vitreous for quartz; Crystal Structure: Isometric (cubes) and Trigonal; Cleavage: Indistinct; Specific Gravity: 4.9-5.2 (Pyrite), 2.65 (Quartz)

Hardness: 6-6
Luster: Metallic for pyrite, vitreous for quartz

Identified March 20, 2026More mineral →

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Physical properties

Formation & geological history

Formed through hydrothermal processes where hot, mineral-rich fluids circulate through fractures in existing rock. As the fluids cool, the minerals precipitate out. This can occur across various geological ages from the Precambrian to the Cenozoic, often in association with metamorphic or igneous activity.

Uses & applications

Primary source of sulfur and sulfuric acid in industry; quartz is used in glassmaking and electronics. As a specimen, it is popular for collectors and as a lapidary material for jewelry like cabochons.

Geological facts

Pyrite is famously known as 'Fool's Gold' due to its resemblance to precious metals. During the 16th and 17th centuries, it was used as a spark source in wheel-lock firearms. Quartz is the second most abundant mineral in Earth's continental crust.

Field identification & locations

Identify in the field by the high-contrast 'gold-on-white' appearance. Pyrite has a black-greenish streak when rubbed on a streak plate, unlike real gold which has a yellow streak. Common in mining belts like those in Colorado, Peru, China, and Spain. Tips: Look for cubic crystal shapes in the metallic areas.

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