Rock Identifier

sedimentary or metamorphic

Sandstone or Quartzite Pebble

Arenite or Quartzite

AI-generated identification · may be incorrect

Hardness: 6-7 (Mohs scale), Color: Brown, tan, earthy tones, Luster: Dull to slightly waxy from smoothing, Texture: Fine-grained, rounded by water action.

Identified September 19, 2026More sedimentary or metamorphic →

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Physical properties

Hardness: 6-7 (Mohs scale), Color: Brown, tan, earthy tones, Luster: Dull to slightly waxy from smoothing, Texture: Fine-grained, rounded by water action.

Formation & geological history

Formed from compressed sand (sedimentary sandstone) or metamorphosed sandstone (quartzite), then rounded through mechanical weathering in a river or beach environment over long periods of time.

Uses & applications

Used in landscaping, decorative stone, and as a worry stone or tactile object. Commercially, sandstones are used for construction.

Geological facts

River rocks and beach pebbles get their smooth, rounded shapes from constant tumbling in moving water, which grinds off rough edges.

Field identification & locations

Identified by its granular texture (often visible under a lens) and smooth, rounded shape. Very common in riverbeds and coastal areas.

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Other sedimentary or metamorphic specimens

Natural freshwater pearls (Pearl (nacreous calcium carbonate; chiefly aragonite, CaCO₃)) — gemstone

Natural freshwater pearls

Pearl (nacreous calcium carbonate; chiefly aragonite, CaCO₃)

Dark gray rounded river pebble (Likely basalt or fine-grained volcanic rock; exact identification requires testing) — igneous

Dark gray rounded river pebble

Likely basalt or fine-grained volcanic rock; exact identification requires testing

Weathered dark stone, possibly basalt (Basalt; commonly plagioclase feldspar, pyroxene, and minor olivine) — igneous

Weathered dark stone, possibly basalt

Basalt; commonly plagioclase feldspar, pyroxene, and minor olivine

Painted River Rock (Artificially Coated Sedimentary Rock) — sedimentary

Painted River Rock

Artificially Coated Sedimentary Rock

Red coral (coral beads) (Precious coral, usually Corallium spp.; composed primarily of calcium carbonate (calcite)) — gemstone

Red coral (coral beads)

Precious coral, usually Corallium spp.; composed primarily of calcium carbonate (calcite)

Tumbled milky quartz (Quartz, SiO₂; trigonal crystal system) — mineral

Tumbled milky quartz

Quartz, SiO₂; trigonal crystal system