metamorphic
Weathered quartz-rich pebble
Quartzite or silicified sandstone; predominantly microcrystalline quartz (SiO₂)
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; gray, cream, and tan with fine granular texture, dull to slightly silky luster, and no obvious cleavage. The layered, fractured appearance may reflect bedding or veining, while the rounded shape indicates water wear.
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Physical properties
Hardness about 6.5–7 Mohs; gray, cream, and tan with fine granular texture, dull to slightly silky luster, and no obvious cleavage. The layered, fractured appearance may reflect bedding or veining, while the rounded shape indicates water wear.
Formation & geological history
Likely a silica-cemented sandstone metamorphosed into quartzite, or strongly silicified sedimentary rock; exact age and origin cannot be established from the photograph. Formed through burial, compaction, silica cementation, and/or heat-pressure recrystallization, then exposed by erosion.
Uses & applications
Quartzite is used as durable aggregate, building stone, paving, and decorative material; attractive pebbles are collected but usually have modest commercial value.
Geological facts
Quartz-rich rocks resist weathering, so they commonly survive as rounded stream or beach pebbles. The pale vein-like bands could be quartz veins or remnants of sedimentary layering.
Field identification & locations
Identify with a scratch test: it should scratch ordinary glass and resist a steel knife; it typically shows no reaction to dilute hydrochloric acid. Common in streambeds, beaches, and terrains containing sandstone or quartz veins.
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