Rock Identifier
Milky Quartz (Water-worn Pebble) (Quartz (Silicon Dioxide, SiO2)) — mineral
mineral

Milky Quartz (Water-worn Pebble)

Quartz (Silicon Dioxide, SiO2)

Hardness: 7.0 on Mohs scale; Color: Opaque white to translucent; Luster: Vitreous to waxy (when polished by water); Crystal Structure: Trigonal (hexagonal system); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness
7
Color
Opaque white to translucent
Luster
Vitreous to waxy (when polished by water)
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Physical properties

Hardness: 7.0 on Mohs scale; Color: Opaque white to translucent; Luster: Vitreous to waxy (when polished by water); Crystal Structure: Trigonal (hexagonal system); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed through hydrothermal activity or cooling of silica-rich magma/lava. This specific specimen is a 'clast' that has been eroded from a larger vein and tumbled smooth by water action in a river or beach environment over thousands of years.

Uses & applications

Industrial uses include glassmaking, abrasives, and electronics (due to piezoelectric properties). In jewelry, it is used for beads, cabochons, and tumble-polishing for decorative landscaping or 'healing crystals'.

Geological facts

Milky quartz gets its cloudy white appearance from tiny fluid inclusions of gas or liquid trapped during crystal growth. It is the most common variety of crystalline quartz found on Earth's surface.

Field identification & locations

Identify in the field by its inability to be scratched by a steel knife (7.0 hardness), its lack of cleavage planes, and its white, 'milky' opacity. It is found globally in almost all geological environments, particularly in gravel beds and along coastlines.

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