sedimentary

Sandstone (specifically Double Arch in Arches National Park)

Entrada Sandstone

AI-generated identification · may be incorrect

Hardness: 6-7 (based on quartz content); Color: Red, orange, tan; Luster: Dull/Earthy; Structure: Clastic, fine-grained; Composition: Predominantly quartz grains with iron oxide (hematite) cement.

Hardness: 6-7 (based on quartz content)
Color: Red, orange, tan
Luster: Dull/Earthy

Identified April 2, 2026More sedimentary →

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Physical properties

Hardness: 6-7 (based on quartz content); Color: Red, orange, tan; Luster: Dull/Earthy; Structure: Clastic, fine-grained; Composition: Predominantly quartz grains with iron oxide (hematite) cement.

Formation & geological history

Formed during the Jurassic period (approx. 150-200 million years ago) from ancient sand dunes. The arches are created by differential weathering and erosion, specifically salt tectonics and frost wedging.

Uses & applications

Primary use is tourism and aesthetic conservation. Sandstone generally is used in construction as building stone and grit for grinding.

Geological facts

Double Arch is a 'pothole' arch, formed by water erosion from above rather than side-to-side. It was a filming location for the opening scene of 'Indiana Jones and the Last Crusade'.

Field identification & locations

Identify by its distinct reddish-orange hue and cross-bedding layers. Found commonly in the Colorado Plateau. Collectors can look for small tumbled samples or decorative slabs.