Mineral

Quartz Pebble (River Rock)

Silicon Dioxide (SiO₂)

Hardness: 7 on Mohs scale; Color: Milky white to translucent; Luster: Vitreous to greasy; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 7 on Mohs scale
Color: Milky white to translucent
Luster: Vitreous to greasy

Identified March 12, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale; Color: Milky white to translucent; Luster: Vitreous to greasy; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Formation & geological history

Formed from the crystallization of silica-rich magma or precipitation from hydrothermal veins. This specimen shows significant rounding and smoothing due to fluvial (river) or glacial erosion over thousands to millions of years.

Uses & applications

Primary source of silica for glassmaking and electronics; used in construction as aggregate; popular for landscaping, lapidary tumbling, and as a common find for amateur rock collectors.

Geological facts

Quartz is the second most abundant mineral in Earth's continental crust. This specific 'milky' appearance is caused by tiny fluid inclusions of gas or liquid trapped during the crystal's growth.

Field identification & locations

Identify in the field by its ability to scratch glass and lack of reaction to acid. Commonly found in riverbeds, beaches, and glacial till globally. Collectors should look for unique inclusions or water-worn shapes.