metamorphic

Weathered iron-stained quartzite or sandstone cobble

Quartzite (quartz-rich rock), possibly ferruginous sandstone

AI-generated identification · may be incorrect

Likely composed mainly of quartz with iron-oxide coatings and minor feldspar/clay. Mohs hardness about 6.5–7 if quartzite; dull to earthy, tan-brown, massive, with no obvious cleavage and moderate-to-high density.

Identified August 8, 2026More metamorphic →

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Physical properties

Formation & geological history

Probably a naturally rounded river or beach cobble formed by abrasion and weathering. If quartzite, its original sandstone was metamorphosed during a mountain-building event; exact age and origin cannot be determined from the photograph.

Uses & applications

Common quartzite is used as aggregate, road stone, landscaping rock, and occasionally building stone; attractive pieces may be collected but are generally low-value.

Geological facts

The rusty coloration is characteristic of oxidized iron minerals such as hematite or goethite. The rounded shape indicates transport by water, ice, or prolonged surface abrasion.

Field identification & locations

Look for a gritty or sugary quartz texture, translucent grains, and resistance to scratching by a steel knife; quartz-rich material should scratch glass. Common worldwide in river gravels and quartzite-bearing mountain regions; definitive identification requires a fresh break or hardness test.