metamorphic

Rounded river pebble, likely quartzite

Quartzite (quartz-rich rock; identification from appearance is provisional)

AI-generated identification · may be incorrect

Smooth, rounded, mottled gray-brown with a fine, slightly sparkly surface; likely Mohs hardness about 7, vitreous to dull luster, and no obvious cleavage. Quartzite is chiefly interlocking quartz crystals; the specimen’s exact composition cannot be confirmed visually.

Identified October 4, 2026More metamorphic →

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Physical properties

Formation & geological history

Quartzite forms when quartz-rich sandstone is recrystallized by heat and pressure during metamorphism. The pebble’s rounding suggests transport by flowing water, but its geological age and source are unknown.

Uses & applications

Commonly collected as a natural specimen or used in landscaping; quartzite is also used as building stone and aggregate.

Geological facts

Quartzite is typically much harder and more resistant to weathering than its sandstone precursor.

Field identification & locations

Look for a hard, gritty-to-sugary texture and quartz grains fused together; it should resist scratching by a steel knife. Quartzite pebbles occur in river and beach gravels worldwide.