metamorphic

Rounded quartz-rich pebble, likely quartzite

Quartzite (microcrystalline quartz, SiO₂), possibly quartz-rich sandstone

AI-generated identification · may be incorrect

Off-white, opaque, fine-grained and weakly sugary with a dull to faintly vitreous luster; quartz hardness is about 7 Mohs, with no obvious cleavage. Brown-red streaks are likely iron-oxide staining; the rounded form indicates stream or beach abrasion.

Identified September 15, 2026More metamorphic →

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Physical properties

Formation & geological history

Quartzite forms when quartz sandstone is metamorphosed and recrystallized under heat and pressure, commonly during mountain-building; its exact geological age cannot be determined from the photograph. If sedimentary instead, it is cemented quartz sand.

Uses & applications

Common quartzite is used as crushed stone, aggregate, building or decorative stone, and landscaping material; this ordinary rounded pebble has little commercial value.

Geological facts

Quartzite is very resistant to weathering and typically scratches glass, unlike calcite-rich rocks. Iron oxides such as hematite or limonite commonly create rusty red-brown patches.

Field identification & locations

Test with a steel knife and glass: quartzite should resist the knife and scratch glass; dilute hydrochloric acid should not fizz. Common sources include metamorphic mountain belts and quartz-rich river gravels worldwide.