mineral

Quartz Cobble (with Iron Staining)

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs), Color: Yellowish-tan due to iron oxide staining over translucent white, Luster: Vitreous to greasy, Crystal Structure: Trigonal, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Identified April 6, 2026More mineral →

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Physical properties

Formation & geological history

Formed from hydrothermal veins or as a primary constituent of igneous rocks. This specific specimen is likely a water-worn river cobble that has undergone mechanical weathering and subsequent chemical staining from iron-rich groundwater or soil.

Uses & applications

Primarily used as industrial aggregate, in glass manufacturing, or as a decorative landscaping stone. In smaller, purer forms, quartz is used for electronics and jewelry.

Geological facts

Quartz is the second most abundant mineral in Earth's continental crust. Iron staining can produce varied hues from light yellow (limonite) to deep red (hematite) on the surface of otherwise colorless quartz.

Field identification & locations

Identified by its high hardness (scratches glass), lack of cleavage, and waxy/vitreous luster on fresh breaks. Found globally in riverbeds, glacial tills, and outcrops. Common for amateur collectors to find while rockhounding.

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