sedimentary

Tumbled quartz-rich sandstone

Quartz arenite (siliciclastic sandstone), likely iron-stained

AI-generated identification · may be incorrect

Identified August 29, 2026More sedimentary →

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Physical properties

Composed mainly of quartz grains with possible feldspar and iron-oxide cement; Mohs hardness about 6–7 for quartz grains, tan-brown color, dull to sugary/vitreous luster, granular texture, and no prominent cleavage. The rounded shape appears human-tumbled or naturally abraded, with crystalline quartz patches visible on the surface.

Formation & geological history

Formed when sand accumulated, compacted, and cemented—probably by silica and iron oxides—then weathered and rounded. Its exact geological age cannot be determined from the image; sandstone ranges from Precambrian to recent formations.

Uses & applications

Used as building and paving stone, aggregate, and decorative material; attractive pieces may be sold as lapidary or teaching specimens. Typical value is low unless unusually patterned or crystalline.

Geological facts

The sparkling areas likely reflect exposed quartz grains or drusy silica rather than a separate gemstone. Iron oxides produce the rusty brown coloration.

Field identification & locations

Identify it by visible sand-sized grains, gritty texture, quartz sparkle, and lack of the uniform glassy appearance of quartzite. Common in sedimentary basins worldwide; vinegar will not fizz unless carbonate cement is present.