mineral

Quartz (River Cobble)

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: White to tan with iron staining (orange/brown); Luster: Vitreous to waxy; Crystal structure: Trigonal; Cleavage: None/Conchoidal fracture.

Hardness: 7 (Mohs scale)
Color: White to tan with iron staining (orange/brown)
Luster: Vitreous to waxy

Identified April 11, 2026More mineral →

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Physical properties

Hardness: 7 (Mohs scale); Color: White to tan with iron staining (orange/brown); Luster: Vitreous to waxy; Crystal structure: Trigonal; Cleavage: None/Conchoidal fracture.

Formation & geological history

Formed from silica-rich hydrothermal fluids or within igneous and metamorphic rocks. This specific specimen is a 'river cobble,' rounded by mechanical erosion in water over thousands of years.

Uses & applications

Used in glass manufacturing, electronics, abrasives, and as decorative gravel. In this worn state, it is primarily a collector's curiosity or used in landscaping.

Geological facts

Quartz is the second most abundant mineral in Earth's continental crust. Its grains can survive long-distance transport in rivers due to its extreme chemical and physical stability.

Field identification & locations

Identify in the field by its inability to be scratched by a steel knife and its lack of cleavage. Commonly found in riverbeds, glacial deposits, and beaches globally.