metamorphic
Water-worn pebble, likely quartz-rich sandstone or quartzite
Quartzite (tentative; a photograph cannot confirm whether the grains are fused or cemented)
AI-generated identification · may be incorrectRounded, gray pebble with a pale, sparkly surface, likely dominated by quartz (Mohs 7); quartz has a vitreous luster and no cleavage. Grain size and specific gravity cannot be reliably determined from the image.
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Physical properties
Rounded, gray pebble with a pale, sparkly surface, likely dominated by quartz (Mohs 7); quartz has a vitreous luster and no cleavage. Grain size and specific gravity cannot be reliably determined from the image.
Formation & geological history
If quartzite, it formed when quartz sandstone was recrystallized under heat and pressure; if sandstone, its grains were cemented during burial. Its rounded shape indicates abrasion during transport by water; its age and original location are unknown.
Uses & applications
A small pebble is mainly suitable for collecting or decoration; quartz-rich stone is also used as aggregate and, when suitable, building stone.
Geological facts
Quartz-rich pebbles can look similar whether they are sandstone or quartzite; a broken surface and grain-boundary inspection can help distinguish them.
Field identification & locations
Look for visible grains and whether they break apart at grain boundaries: quartzite tends to fracture through grains, while sandstone commonly breaks around them. Such pebbles occur in riverbeds, beaches, and glacial deposits.
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