sedimentary

Spheroidal weathered sandstone boulder

Quartz-rich sandstone; commonly arkose or quartz arenite

AI-generated identification · may be incorrect

Typically Mohs hardness 6–7, tan to rusty brown, earthy to slightly gritty luster, and composed of cemented sand grains with little cleavage. The rounded form and surface cracking reflect weathering rather than crystal structure.

Identified August 24, 2026More sedimentary →

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Physical properties

Formation & geological history

A sedimentary sandstone formed when sand was buried, compacted, and cemented—usually tens to hundreds of millions of years ago. Its near-spherical shape likely developed by concentric weathering of a jointed outcrop or transported boulder.

Uses & applications

Used as landscape stone, garden boulders, retaining-wall material, and architectural stone; generally low jewelry value.

Geological facts

The pronounced rounded shape is called spheroidal or onion-skin weathering. Iron-oxide staining produces the orange-brown color, while dark patches may be lichen, soil, or weathered cement.

Field identification & locations

Identify it by visible sand grains, gritty texture, tan coloration, lack of crystal cleavage, and acid-insensitive quartz-rich composition. Common in sedimentary basins, glacial deposits, stream gravels, and eroding sandstone terrains.