Sandstone with Algae Growth

Physical Properties

Hardness: 6-7 (individual quartz grains); Color: Tan/Brown basics with green surface staining; Luster: Dull/Earthy; Structure: Granular/Clastic; Porous texture.

Formation & Geological History

Formed through the accumulation and cementation of mineral particles (lithification) in river, lake, or ocean environments. The green coloring is a biological biofilm formed by moisture and light exposure after erosion.

Uses & Applications

Common industrial use in building material, road gravel, and glass manufacturing. This specific small weathered specimen is generally for amateur collecting.

Geological Facts

Sandstone is one of the most common sedimentary rocks on Earth. The green stripes on this specimen are likely not mineral bands like malachite, but rather organic 'endolithic' algae or lichen growing into the bedding planes.

Field Identification & Locations

Identify by its 'sandpaper' feel and visible grains. Often found in riverbeds or landscaping gravel. Check if green parts scrape off or turn brown when dried to confirm organic growth vs mineral.

Identified on: 4/26/2026

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