sedimentary
Sandstone (Quartzose Sandstone)
Clastic sedimentary rock (SiO2 primary composition)
Hardness: 6-7 (Mohs scale); Color: Tan, buff, or light brown due to iron oxides; Luster: Dull to earthy; Crystal structure: Primarily granular (clastic) with visible sand grains; Cleavage: None (fractures around grains); Specific gravity: 2.2-2.8.
- Hardness
- 6-7 (Mohs scale)
- Color
- Tan, buff, or light brown due to iron oxides
- Luster
- Dull to earthy
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Tan, buff, or light brown due to iron oxides; Luster: Dull to earthy; Crystal structure: Primarily granular (clastic) with visible sand grains; Cleavage: None (fractures around grains); Specific gravity: 2.2-2.8.
Formation & geological history
Formed through the accumulation and cementation of sand-sized mineral grains or rock fragments. This specimen appears to be a water-worn river cobble. It likely formed in a high-energy environment like a beach, desert, or riverbed millions of years ago, then was smoothed by glacial or fluvial transport.
Uses & applications
Used extensively in the construction industry as building stone, pavers, and crushed aggregate. Purer forms are used as a source of silica for glassmaking. Small smooth cobbles like this are often used in landscaping and xeriscaping.
Geological facts
Sandstone accounts for about 10-25% of all sedimentary rocks on Earth. It is a vital reservoir rock for groundwater, oil, and natural gas due to its porosity and permeability. Famous formations include the Antelope Canyon in Arizona and the red sandstone of Petra, Jordan.
Field identification & locations
Identify in the field by its 'gritty' feel (like sandpaper) and visible rounded grains. It is commonly found in riverbeds, coastal regions, and sedimentary basins globally. Collectors look for unique banding or fossil inclusions.
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