sedimentary
River Stone (Sedimentary Sandstone/Quartzite)
Arenite/Quartzite transition specimen
Hardness: 6-7 Mohs; Color: Brownish-grey with reddish iron staining; Luster: Dull/Earthy; Structure: Fine-grained clastic; Cleavage: None; Shape: Well-rounded (sub-spherical).
- Hardness
- 6-7 Mohs
- Color
- Brownish-grey with reddish iron staining
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 Mohs; Color: Brownish-grey with reddish iron staining; Luster: Dull/Earthy; Structure: Fine-grained clastic; Cleavage: None; Shape: Well-rounded (sub-spherical).
Formation & geological history
Formed via the accumulation and cementation of sand-sized mineral grains or rock fragments, followed by extensive fluvial erosion in a river or stream bed over thousands of years as the rock was transported downstream.
Uses & applications
Commonly used in landscaping, decorative ground cover, construction aggregate, and as 'worry stones' for amateur collectors.
Geological facts
The smooth, rounded shape is the result of 'abrasion'—a process where rocks bang against each other in moving water, wearing down sharp edges. This specific specimen shows 'desert varnish' or iron-oxide staining on the surface.
Field identification & locations
Identify by its smooth texture and rounded edges. Found abundantly in riverbeds, glacial tills, and beaches. Collectors look for unique patterns or unusually smooth symmetry.
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