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

River Pebble (Quartzite or Chert)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs), Color: Gray and yellow/tan, Luster: Waxy to dull, Crystal Structure: Microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7

Hardness
6
Identified More metamorphic or sedimentary →
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Physical properties

Hardness: 6.5-7 (Mohs), Color: Gray and yellow/tan, Luster: Waxy to dull, Crystal Structure: Microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the metamorphism of sandstone (quartzite) or the accumulation of silica in sedimentary environments (chert). This specific pebble has been smoothed and rounded by water erosion in a river or coastal environment.

Uses & applications

Common river stones are used for landscaping, decorative gravel, aquarium substrate, and small-scale ornamental crafts.

Geological facts

The yellow banding suggests iron oxide staining. River pebbles illustrate the rock cycle by showing how larger rock masses are physically weathered over centuries into smooth, rounded shapes.

Field identification & locations

Identify by its rounded, smooth texture and high hardness (cannot be scratched by a steel knife). Commonly found in riverbeds, glacial deposits, and beaches globally.

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Small quartz-rich mineral fragment

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mineral
Quartz vein fragment (Quartz, silicon dioxide (SiO₂), likely milky to translucent quartz with iron-oxide or clay inclusions) — mineral

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Quartz, silicon dioxide (SiO₂), likely milky to translucent quartz with iron-oxide or clay inclusions

mineral
Quartz-rich rock, possibly milky quartz or quartzite (Quartz (SiO₂); if quartzite, recrystallized quartz sandstone) — metamorphic

Quartz-rich rock, possibly milky quartz or quartzite

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metamorphic
Tumbled quartz pebble, possibly citrine or pale smoky quartz (Quartz (SiO₂), likely microcrystalline/tumbled material) — mineral

Tumbled quartz pebble, possibly citrine or pale smoky quartz

Quartz (SiO₂), likely microcrystalline/tumbled material

mineral
Unidentified greenish-gray rock fragment (Tentatively altered basalt or basaltic volcanic rock; mineral identification requires testing) — igneous

Unidentified greenish-gray rock fragment

Tentatively altered basalt or basaltic volcanic rock; mineral identification requires testing

igneous