sedimentary

Weathered sandstone or quartzite cobble

Quartz-rich sandstone, possibly weakly metamorphosed to quartzite (SiO₂-rich)

AI-generated identification · may be incorrect

Tan-brown, dull to weakly silky surface with fine granular texture and iron-oxide staining; likely hardness 6–7, massive/nonfoliated, with indistinct cleavage and specific gravity about 2.6. The rounded shape and shallow pits indicate natural abrasion and weathering.

Identified September 3, 2026More sedimentary →

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Physical properties

Formation & geological history

Most likely lithified quartz sand deposited in an ancient river, beach, or shallow-marine setting, then cemented by silica or iron oxides; if quartzitic, later heat and pressure recrystallized it. Exact geological age cannot be determined from the photograph.

Uses & applications

Common sandstone is used as building stone, paving, aggregate, and decorative material; quartzite is valued for durable slabs, flooring, and landscaping. This specimen has modest collector value unless its locality or provenance is notable.

Geological facts

Quartz-rich rocks commonly survive erosion and become rounded stream or beach cobbles. Brown coloration typically comes from hematite or limonite coatings rather than the primary quartz.

Field identification & locations

Look for gritty grains and cement in sandstone versus an interlocking sugary quartz texture that scratches glass in quartzite; a vinegar test is usually negative. Common worldwide in sedimentary basins, river gravels, and metamorphic terrains.