Sandstone (with Lichen)

Physical Properties

Hardness: 6-7 (Mohs scale for quartz grains); Color: Tan, grey, and brown with white/green surface lichen; Luster: Dull/Earthy; Crystal structure: Clastic (granular); Cleavage: None (fractures around grains)

Formation & Geological History

Formed through the accumulation and cementation of sand-sized mineral grains or rock fragments, typically in riverbeds, deserts, or marine environments over millions of years (often Paleozoic to Mesozoic era).

Uses & Applications

Commonly used as a building material, flagstone for landscaping, glass manufacturing (if high silica), and as a reservoir rock for oil and gas.

Geological Facts

Sandstone makes up about 20% of all sedimentary rocks on Earth. This specific specimen is host to crustose lichen, which contributes to biological weathering over time.

Field Identification & Locations

Identify in the field by its 'gritty' feel (like sandpaper) and visible bedding planes. Common in arid regions and coastal cliffs. Check for reaction with HCl; if it fizzes, it has a calcitic cement.

Identified on: 4/25/2026

Mode: Standard