sedimentary

Weathered quartz-rich sandstone (likely ferruginous sandstone)

Quartz arenite to subarkose; mainly SiO₂ quartz with iron-oxide cement

AI-generated identification · may be incorrect

Rounded, brown-to-cream pebble with granular texture and rusty orange staining. Quartz is Mohs ~7; sandstone is typically ~6–7, with earthy to dull luster, no cleavage, and variable porosity. Individual grains are only weakly visible in the photo.

Identified September 11, 2026More sedimentary →

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Physical properties

Formation & geological history

Lithified sand cemented by silica and iron oxides, then rounded by transport and weathering. Exact age cannot be determined visually; sandstone is common in sedimentary basins and river gravels.

Uses & applications

Used as building stone, paving and aggregate; attractive pieces may be collected, but this specimen has modest commercial value.

Geological facts

The reddish-brown color is characteristic of hematite/goethite coatings or cement. Its rounded shape indicates abrasion in a stream, gravel deposit, or weathered conglomeratic layer.

Field identification & locations

Likely identification is based on its granular, noncrystalline appearance and iron staining. Near 22.0°S, 63.7°W, sedimentary rocks and transported Andean foreland gravels make this plausible. A hand lens, streak test, and dilute acid test would help distinguish sandstone from weathered quartzite or volcanic rock.