Rock Identifier
Tumbled milky quartz pebble (Quartz (silicon dioxide, SiO₂)) — mineral
mineral

Tumbled milky quartz pebble

Quartz (silicon dioxide, SiO₂)

AI-generated identification · may be incorrect

Typically Mohs hardness 7, white to translucent with a vitreous-to-waxy luster; crystalline structure is trigonal, with no cleavage and conchoidal fracture. The rounded shape indicates natural water-wear or tumbling, while the brown patches may be iron-oxide staining or surface dirt.

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Physical properties

Typically Mohs hardness 7, white to translucent with a vitreous-to-waxy luster; crystalline structure is trigonal, with no cleavage and conchoidal fracture. The rounded shape indicates natural water-wear or tumbling, while the brown patches may be iron-oxide staining or surface dirt.

Formation & geological history

Quartz crystallizes from silica-rich igneous, metamorphic, and hydrothermal fluids; milky varieties contain microscopic fluid or mineral inclusions. Quartz is common throughout Earth’s geologic history, from Precambrian rocks to modern gravels.

Uses & applications

Used in glass, ceramics, electronics, abrasives, and engineered stone; attractive pieces are sold as inexpensive lapidary or display specimens.

Geological facts

It can scratch ordinary glass and steel, but it should not scratch a knife easily. Its white cloudiness results from microscopic inclusions that scatter light.

Field identification & locations

Common in streambeds, beaches, quartz veins, and weathered rock deposits worldwide; identify by hardness, lack of cleavage, conchoidal fracture, and glassy edges. A streak test is white.

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