mineral

Milky Quartz Pebble

Crystalline Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Milky white with iron staining; Luster: Vitreous to greasy; Crystal Structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Milky white with iron staining
Luster: Vitreous to greasy

Identified February 26, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale; Color: Milky white with iron staining; Luster: Vitreous to greasy; Crystal Structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed from silica-rich hydrothermal fluids or within igneous pegmatites. This specific specimen has been tumbled and rounded by alluvial (water-based) erosion after weathering out of larger veins or rock formations.

Uses & applications

Used as a gemstone (cabochons), for glass manufacturing, and as decorative landscaping aggregate. In high-purity forms, it provides silicon for electronics.

Geological facts

The milky appearance is caused by microscopic inclusions of fluids or gases trapped during the crystal's growth. It is the most common mineral found on Earth's continental surface.

Field identification & locations

Identified in the field by its hardness (scratches glass), white streak, and lack of cleavage. Often found in riverbeds, glacial deposits, and mountain outcrops globally.

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