sedimentary
Sandstone Concretion
Clastic sedimentary rock (primarily Quartz SiO2 with mineral cement)
Hardness: 6-7 (Mohs); Color: Tan, beige, light grey; Luster: Dull/Earthy; Structure: Clastic, granular texture; Specific Gravity: 2.2-2.8
- Hardness
- 6-7 (Mohs)
- Color
- Tan, beige, light grey
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (Mohs); Color: Tan, beige, light grey; Luster: Dull/Earthy; Structure: Clastic, granular texture; Specific Gravity: 2.2-2.8
Formation & geological history
Formed through the accumulation and cementation of sand-sized mineral grains or rock fragments. Concretions form when mineral cement precipitates within the spaces between grains, often around a nucleus like a leaf or shell.
Uses & applications
Primarily used as a decorative specimen or garden ornament; larger deposits are used in construction, road base, and glass making.
Geological facts
Sandstone concretions can sometimes take on biomimetic shapes that resemble bones or artifacts, leading them to be frequently mistaken for fossils or ancient tools.
Field identification & locations
Identify by its gritty sandpaper feel and visible grains. Found in sedimentary basins and riverbeds worldwide. Look for unusual rounded or elongated shapes weathering out of cliffs.
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