mineral

Quartz (Iron-stained)

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: typically white, clear, or tan but stained reddish-brown by iron oxides; Luster: Vitreous (glassy); Crystal Structure: Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Hardness: 7 on Mohs scale
Luster: Vitreous (glassy)

Identified April 12, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the cooling of silica-rich magma or from hydrothermal veins. The iron staining occurs when the specimen is exposed to groundwater containing dissolved iron, which precipitates as limonite or hematite into micro-cracks.

Uses & applications

Used in glassmaking, electronics, and watchmaking (piezoelectric properties). Iron-stained quartz is a common indicator mineral for gold prospectors, as both often precipitate in the same hydrothermal vein systems.

Geological facts

Quartz is the second most abundant mineral in Earth's continental crust. Prospectors call iron-stained quartz 'rusty quartz' and it is often crushed to check for 'free-milling' gold trapped inside.

Field identification & locations

Identify in the field by its hardness (it will scratch glass and steel) and lack of cleavage. Look for the 'sugary' texture and characteristic orange-red staining in riverbeds or near mountain outcrops.