sedimentary

Weathered feldspathic sandstone

Quartz–feldspar sandstone (arkose), with iron-oxide staining

AI-generated identification · may be incorrect

Hardness about 6–7 for quartz grains; tan to brown, earthy appearance, dull to weakly gritty luster, and no obvious cleavage as a whole rock. Visible coarse sand-sized grains and porous, crumbly texture suggest arkosic sandstone.

Identified August 31, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when feldspar- and quartz-rich sediment accumulated, compacted, and cemented, commonly in alluvial fans or braided-river deposits; its exact geological age cannot be determined from the photograph.

Uses & applications

Used locally as building or landscaping stone and is mainly a teaching or collecting specimen; friable pieces have little commercial value.

Geological facts

The brown coloration likely comes from iron oxides produced during weathering. Feldspar-rich sandstone weathers relatively quickly into clay compared with quartz-rich sandstone.

Field identification & locations

Identify it by gritty sand grains, layered or granular texture, and inability to scratch individual quartz grains with a steel nail; acid testing is generally negative unless carbonate cement is present. Common worldwide in continental sedimentary basins.