metamorphic

Rounded greenish-gray pebble, likely quartzite

Quartzite (mostly crystalline quartz, SiO₂); identification is provisional from the image

AI-generated identification · may be incorrect

Fine-grained, rounded, dull to slightly granular surface with pale green, tan, and gray mottling. Quartz has Mohs hardness 7 and a trigonal crystal structure; the pebble’s hardness and cleavage cannot be confirmed visually.

Identified October 15, 2026More metamorphic →

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Physical properties

Formation & geological history

Quartzite forms when quartz-rich sandstone is recrystallized by heat and pressure, typically during regional metamorphism. Its age and source environment cannot be determined from the photograph.

Uses & applications

Commonly used as landscaping stone, aggregate, and decorative material; attractive pieces may be collected or used in lapidary work.

Geological facts

Quartzite is typically tougher than its sandstone precursor because recrystallized quartz grains interlock.

Field identification & locations

Look for a hard, quartz-rich stone with a sugary or fused texture and no obvious sand grains; a scratch test against glass can help. Rounded pebbles occur in river and beach gravels worldwide.