sedimentary

Sandstone

Arenicola (comprising mostly Quartz, SiO2)

Hardness: 6-7 (Mohs scale); Color: Tan, reddish-brown, buff; Luster: Dull or earthy; Crystal structure: Clastic (composed of sand-sized grains); Cleavage: None (grains are cemented); Specific gravity: 2.2-2.8

Hardness: 6-7 (Mohs scale)
Color: Tan, reddish-brown, buff
Luster: Dull or earthy

Identified March 22, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the lithification of sand-sized grains of mineral, rock, or organic material. These grains are deposited in environments like deserts, beaches, or riverbeds and cemented together over millions of years by minerals like silica or calcium carbonate.

Uses & applications

Commonly used in construction as a building stone (dimension stone), pavers, and decorative landscaping boulders. Historically used for grinding stones and sculptures.

Geological facts

Sandstone makes up about 20% to 25% of all sedimentary rocks on Earth. The iconic red color in many specimens (like those in the US Southwest) is caused by the oxidation of iron minerals within the rock, effectively 'rusting'.

Field identification & locations

Identify in the field by its distinctive 'sandpaper' feel and visible layers (bedding planes). It is commonly found in dried-up riverbeds, canyons, and coastal cliffs. Collectors should look for cross-bedding or fossil inclusions.

Other sedimentary specimens

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Sandstone or Siltstone

Arenite (if sandstone)

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Shale or Slaty Mudstone

Argillaceous sedimentary rock

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Sandstone

Arenite (primarily SiO2)

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Chert Breccia

Brecciated Chert (Microcrystalline Silica)

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Sandstone (Quartz-rich)

Arenite (SiO2)

sedimentary

Sandstone (with man-made markings)

Arenite (composed primarily of Quartz, SiO2)

sedimentary