mineral

Milky Quartz Cobble

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: Opaque white to slightly translucent; Luster: Vitreous to greasy; Crystal Structure: Hexagonal (trigonal); Cleavage: Conchoidal fracture (no cleavage); Specific Gravity: 2.65.

Hardness: 7 (Mohs scale)
Color: Opaque white to slightly translucent
Luster: Vitreous to greasy

Identified March 27, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the cooling of molten silica in hydrothermal veins or as a primary constituent of igneous rocks like granite. This specimen appears water-worn, likely tumbled in a river or coastal environment during the Quaternary period.

Uses & applications

Used industrially in glass manufacturing, as an abrasive, and in the production of silicon wafers for electronics. Tumbled specimens are used in landscaping and as low-cost decorative stones.

Geological facts

The 'milky' appearance is caused by tiny inclusions of gas or liquid trapped during the crystal's growth. It is one of the most common and resistant minerals on Earth's crust.

Field identification & locations

Identify in the field by its ability to scratch glass and its lack of cleavage planes. Found globally in riverbeds, beaches, and mountain outcrops. Collectors look for pieces with unique textures or associated minerals.