sedimentary
Sandstone (Quartzite-rich Cobble)
Clastic sedimentary rock (primarily SiO2)
Hardness: 6-7 on Mohs scale; Color: Tan, beige, or light brown with iron staining; Luster: Dull/Earthy; Crystal structure: Granular/Clastic; Cleavage: None (conchoidal to irregular fracture); Specific gravity: 2.2 - 2.8
- Hardness
- 6-7 on Mohs scale
- Color
- Tan, beige, or light brown with iron staining
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Tan, beige, or light brown with iron staining; Luster: Dull/Earthy; Crystal structure: Granular/Clastic; Cleavage: None (conchoidal to irregular fracture); Specific gravity: 2.2 - 2.8
Formation & geological history
Formed through the accumulation and cementation of mineral particles or rock fragments, typically sand-sized grains of quartz. This particular specimen is a water-worn cobble, indicating it spent time in a high-energy fluvial environment (river) or beach before deposition.
Uses & applications
Commonly used as construction aggregate, landscaping stones (river rock), and in some cases as dimension stone for building. Highly durable varieties are used as glass-making silica if purity is high.
Geological facts
Sandstone is one of the most common sedimentary rocks on Earth, making up nearly 20% of all sedimentary rock on the planet. Its rounded shape is a result of mechanical weathering through a process called 'attrition' during transport in water.
Field identification & locations
Identify in the field by its sandy texture (it may feel like sandpaper) and visible grains. It is commonly found in riverbeds, glacial deposits, and coastal regions. For collectors, look for cross-bedding or fossil inclusions.
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