mineral

Quartz / River Cobble

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: White to translucent; Luster: Vitreous to waxy (when river-worn); Crystal Structure: Hexagonal (trigonal); Cleavage: Indistinct/Conchoidal fracture; Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: White to translucent
Luster: Vitreous to waxy (when river-worn)

Identified April 11, 2026More mineral →

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Physical properties

Formation & geological history

Formed from the crystallization of molten magma or precipitation from hydrothermal veins. This specific specimen is a rounded cobble, indicating it has been eroded and smoothed by long-term water transport in a river or stream bed.

Uses & applications

Common industrial uses include glass making, abrasives, and electronics. Rounded river stones of this type are often used in landscaping, decorative masonry, and as low-cost collector specimens.

Geological facts

Quartz is the second most abundant mineral in Earth's continental crust. This specimen shows a 'water-worn' texture, which is a physical record of the geological journey from its source rock to the riverbed.

Field identification & locations

Identify in the field by its hardness (it will scratch glass and steel) and its lack of cleavage (breaks in curved, shell-like patterns). It is ubiquitous in river systems globally.