sedimentary
Sandstone (Quartzose Pebble)
Clastic sedimentary rock (primarily SiO2)
Hardness: 6-7 (Mohs); Color: Grey to tan; Luster: Dull/Earthy; Crystal structure: Granular/Clastic; Cleavage: None; Specific gravity: 2.3–2.4
- Hardness
- 6-7 (Mohs)
- Color
- Grey to tan
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (Mohs); Color: Grey to tan; Luster: Dull/Earthy; Crystal structure: Granular/Clastic; Cleavage: None; Specific gravity: 2.3–2.4
Formation & geological history
Formed from the accumulation and cementation of sand-sized mineral grains or rock fragments. This specific specimen has been significantly smoothed and rounded by water erosion (alluvial or beach transport) over hundreds to thousands of years.
Uses & applications
Common sandstone is used in construction as building stone or crushed for road base. In this rounded form, they are used for decorative landscaping, river rock features, and garden paths.
Geological facts
Sandstone constitutes about 20-25% of all sedimentary rocks. This specimen is a 'clast' which has undergone 'abrasion'—the process by which rocks collide in moving water to lose their sharp edges.
Field identification & locations
Identify in the field by its gritty texture (feels like sandpaper) and visible grains of quartz. It will not fizz with HCl unless it has a calcitic cement. Found globally in riverbeds, beaches, and ancient sedimentary basins.
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