sedimentary

Sandstone (Micaceous)

Arenite (composed primarily of SiO2)

Hardness: 6-7 (Mohs scale) for individual quartz grains; Color: Tan, beige, or yellowish-brown with dark speckles; Luster: Dull or earthy; Crystal structure: Clastic (grainy); Cleavage: None; Specific gravity: 2.2-2.8

Hardness: 6-7 (Mohs scale) for individual quartz grains
Color: Tan, beige, or yellowish-brown with dark speckles
Luster: Dull or earthy

Identified April 11, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation and cementation of sand-sized mineral grains or rock fragments (lithification). Most sandstones are formed in river, lake, or ocean environments over millions of years, often dating from the Paleozoic to the Cenozoic era.

Uses & applications

Primary use in construction (dimension stone), road base, glass manufacturing (if high silica content), and as a reservoir rock for oil and natural gas.

Geological facts

Sandstone makes up about 20% of all sedimentary rocks on Earth. The dark spots visible in this specimen are likely accessory minerals like magnetite or biotite mica trapped during sedimentation.

Field identification & locations

Identify in the field by its gritty, 'sandpaper' texture. If you rub it and sand grains come off, it is sandstone. Commonly found in deserts, riverbeds, and coastal cliffs.

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