Rock Identifier
River Pebble (Likely Quartzite or Chert) (Silicon Dioxide (SiO2)) — metamorphic or sedimentary
metamorphic or sedimentary

River Pebble (Likely Quartzite or Chert)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale), Color: Brownish-tan with weathering, Luster: Dull/Waxy, Crystal Structure: Microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7

Identified More metamorphic or sedimentary →
Explore River Pebble (Likely Quartzite or Chert) in the encyclopedia →

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Physical properties

Hardness: 7 (Mohs scale), Color: Brownish-tan with weathering, Luster: Dull/Waxy, Crystal Structure: Microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the metamorphism of sandstone (quartzite) or precipitation of silica (chert). This specific specimen has been smoothed and rounded by long-term fluvial (river) erosion.

Uses & applications

Commonly used in construction aggregate, landscaping, or as a pocket stone. Harder varieties like this were historically used for making stone tools.

Geological facts

River stones take their smooth, rounded shape from thousands of years of tumbling against other rocks in moving water, a process known as saltation.

Field identification & locations

Identify by its rounded 'potato' shape and inability to be scratched by a steel knife. Commonly found in stream beds, glacial deposits, and beaches.

More like this

Other metamorphic or sedimentary specimens

Likely weathered quartz-bearing rock (uncertain identification) (Possibly quartz-rich granite or granitic aplite; exact identification requires a clearer, larger image and tests) — igneous

Likely weathered quartz-bearing rock (uncertain identification)

Possibly quartz-rich granite or granitic aplite; exact identification requires a clearer, larger image and tests

igneous
Dark gray volcanic rock, probably andesite or basalt (Fine-grained mafic–intermediate volcanic rock; likely basalt (plagioclase ± pyroxene), possibly andesite) — igneous

Dark gray volcanic rock, probably andesite or basalt

Fine-grained mafic–intermediate volcanic rock; likely basalt (plagioclase ± pyroxene), possibly andesite

igneous
Quartz Heart or Arrowhead Shape (Silicon Dioxide (SiO2)) — mineral

Quartz Heart or Arrowhead Shape

Silicon Dioxide (SiO2)

mineral
Quartz (Quartz (SiO2 - Silicon Dioxide)) — Mineral

Quartz

Quartz (SiO2 - Silicon Dioxide)

Mineral
Quartzite (Metamorphic Quartzite (primarily SiO2)) — metamorphic

Quartzite

Metamorphic Quartzite (primarily SiO2)

metamorphic
Milky Quartz (Quartz (Silicon Dioxide, SiO2)) — mineral

Milky Quartz

Quartz (Silicon Dioxide, SiO2)

mineral