mineral

Milky Quartz Pebble

Quartz (Silicon Dioxide, SiO2)

Hardness: 7 on Mohs scale; Color: Cloudy white to opaque; Luster: Vitreous to waxy (when tumbled); Crystal structure: Hexagonal/Trigonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: Cloudy white to opaque
Luster: Vitreous to waxy (when tumbled)

Identified March 25, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale; Color: Cloudy white to opaque; Luster: Vitreous to waxy (when tumbled); Crystal structure: Hexagonal/Trigonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed through the crystallization of silica-rich hydrothermal fluids in veins or as a primary constituent in igneous rocks like granite. Its 'milky' appearance is caused by tiny fluid inclusions of gas or liquid trapped during crystal growth. This specimen appears water-worn, smoothed by fluvial or glacial action over thousands of years.

Uses & applications

Common quartz is used in construction (sand/gravel), as an abrasive, in glassmaking, and in the production of silicon chips. Smooth pebbles are often used in landscaping, aquariums, and as pocket stones or 'worry stones' for collectors.

Geological facts

Milky quartz is the most common variety of crystalline quartz. While it lacks the transparency of rock crystal, it can contain traces of gold in hydrothermal vein deposits. Historically, it was used by many cultures for stone tools due to its hardness and sharp fracture edges.

Field identification & locations

Identify in the field by its inability to be scratched by a steel knife, its lack of cleavage planes, and its characteristic waxy, white appearance. It is ubiquitous globally, commonly found in stream beds, beaches, and eroded mountain soil.