sedimentary

Sandstone cobble

Quartz-rich sandstone, likely arkose or lithic sandstone

AI-generated identification · may be incorrect

A tan, fine- to medium-grained clastic rock with a dull, earthy luster and visibly porous texture. Likely hardness about 6–7 for quartz grains, but it may crumble or scratch more easily because of weak cement; cleavage is absent and specific gravity is roughly 2.2–2.6.

Identified August 21, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when sand-sized grains—commonly quartz, feldspar, and rock fragments—were deposited, compacted, and cemented in an ancient river, dune, beach, or desert environment. Its exact geological age cannot be determined from the photograph.

Uses & applications

Used as building stone, paving, aggregate, and decorative rock; attractive varieties are used for landscaping and architectural facing. This irregular specimen has little commercial value unless unusually patterned or from a documented locality.

Geological facts

The rounded shape and worn surface indicate transport and weathering, likely in a stream or gravel deposit. A fresh broken surface would better reveal grain size, sorting, and cement type.

Field identification & locations

Look for sand-sized grains, bedding, porosity, and a gritty feel; it should not fizz strongly with dilute hydrochloric acid unless carbonate-cemented. Common worldwide, especially in sedimentary basins, river gravels, deserts, and beaches.