sedimentary

Rounded quartz-rich pebble

Likely quartz arenite (quartz sandstone) or quartz-rich metamorphic pebble

AI-generated identification · may be incorrect

Pale cream-gray, fine-grained, matte to slightly sugary luster, with tightly cemented quartz grains; apparent Mohs hardness about 6–7. No visible cleavage; rounded shape reflects stream or beach abrasion, and exact identification requires a close-up or testing.

Identified September 5, 2026More sedimentary →

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Physical properties

Formation & geological history

Probably derived from weathered sandstone or quartzite and naturally rounded in a river, beach, or glacial deposit. The source rock may be hundreds of millions of years old, but the pebble’s present form is much younger.

Uses & applications

As an ordinary pebble it has little industrial or jewelry value, though quartz sandstone is used as aggregate, building stone, and silica source; attractive pieces may be used decoratively.

Geological facts

Quartz-rich rocks commonly resist weathering, producing durable rounded pebbles. A glassy scratch test or acid test can help distinguish quartzite from carbonate rocks.

Field identification & locations

Common worldwide in rivers, beaches, alluvial gravels, and glacial deposits. Quartz grains should scratch glass; dilute hydrochloric acid indicates calcite cement if it fizzes, while a streak or hand lens can reveal grain texture.