sedimentary

Likely weathered sandstone or quartzite

Quartz-rich sandstone; possibly metamorphosed to quartzite (SiO₂-dominant)

AI-generated identification · may be incorrect

Brown-red, fine to medium grained, dull to slightly sparkly, with visible layering and a rough fracture. Quartz-rich sandstone has Mohs hardness about 6–7; quartzite is typically ~7, with no obvious cleavage and specific gravity around 2.6.

Identified August 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Likely deposited as sand, then compacted and cemented; iron oxides produce the reddish-brown color. If quartzite, later burial and metamorphism recrystallized the sandstone. The image does not permit a reliable geological age determination.

Uses & applications

Common sandstone is used for building stone, paving, aggregate, and landscaping; quartzite is used as durable construction stone, countertops, and decorative material. This specimen has little commercial value unless unusually attractive or locally significant.

Geological facts

The layered texture and earthy red-brown color favor sandstone, while a very hard, glassy fracture and fused-looking grains would favor quartzite. The Duluth–northeastern Minnesota region contains abundant Precambrian igneous and metamorphic rocks, so a transported sandstone/quartzite pebble is plausible but not certain.

Field identification & locations

Field tests: inspect grain boundaries with a hand lens, try scratching glass, and apply dilute hydrochloric acid—no fizz is expected. Likely sources include regional glacial deposits or transported river gravel.