sedimentary

Rounded sandstone cobble

Quartz-rich sandstone, likely arkosic or lithic sandstone

AI-generated identification · may be incorrect

Fine- to medium-grained, tan-brown, rounded and naturally smoothed; grains appear sand-sized with scattered darker lithic fragments and a small pebble inclusion. Typical hardness is about 6–7 for quartz grains, with a dull to slightly satin luster; no obvious cleavage or crystal faces.

Identified September 4, 2026More sedimentary →

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Physical properties

Formation & geological history

Lithified sand compacted and cemented by silica, calcite, or iron oxides, then rounded by prolonged water transport such as river or beach action. Its precise geological age cannot be determined from the photograph.

Uses & applications

Primarily a natural curiosity, paperweight, or landscaping stone; sandstone is also widely used as dimension stone, paving, aggregate, and building material. This specimen has little jewelry value.

Geological facts

The elongated shape and uniformly worn surface indicate abrasion in moving water or surf. Brown coloration commonly reflects iron-oxide staining, while the embedded rounded fragment suggests deposition in a mixed-grain sedimentary environment.

Field identification & locations

Identify it by visible sand grains, sedimentary texture, lack of foliation, and rounded water-worn form; a glassy scratch test can confirm quartz-rich grains, though it may damage the specimen. Common environments include streambeds, beaches, and conglomeratic or sandstone-rich terrains.