sedimentary

Sandstone (with biological crust)

Arenite (SiO2 based)

Hardness: 6-7 (individual quartz grains); Color: Buff, tan, with green biological crust; Luster: Dull/Earthy; Crystal structure: Clastic (granular); Cleavage: None (conchoidal fracture on grains); Specific gravity: 2.2-2.8

Hardness: 6-7 (individual quartz grains)
Color: Buff, tan, with green biological crust
Luster: Dull/Earthy

Identified April 10, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation and cementation of sand-sized mineral particles or rock fragments. Often deposited in desert, river, or coastal environments. This specimen shows surface colonization by algae or lichen, indicating recent exposure to moisture and light.

Uses & applications

Commonly used as a building material, in the manufacture of glass (if pure quartz), and as an abrasive in industrial applications.

Geological facts

Sandstone is one of the most common sedimentary rocks on Earth. The green tint seen on this specimen is likely ‘biological soil crust’ or algae, which plays a vital role in preventing erosion in arid climates.

Field identification & locations

Identify by its gritty, sand-paper like texture. Use a magnifying glass to see individual round or angular grains. Commonly found in canyons, riverbeds, and sedimentary basins worldwide.

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