sedimentary
Iron-oxide-cemented sandstone concretion
Ferruginous sandstone concretion, composed mainly of quartz (SiO₂) grains cemented by iron oxides
AI-generated identification · may be incorrectTan-brown, rough and granular, with no visible crystals or cleavage; quartz grains have Mohs hardness 7, though the specimen’s overall hardness varies with cementation. Likely dull to earthy luster; crystal structure is not visible at this scale.
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Physical properties
Tan-brown, rough and granular, with no visible crystals or cleavage; quartz grains have Mohs hardness 7, though the specimen’s overall hardness varies with cementation. Likely dull to earthy luster; crystal structure is not visible at this scale.
Formation & geological history
Formed when mineral-rich groundwater cemented sand grains into a rounded concretion within sediment. Its age and exact formation environment cannot be determined from the image alone.
Uses & applications
Typically collected as a natural curiosity; sandstone is widely used as building stone and aggregate, though this small specimen has no practical industrial use.
Geological facts
Iron oxides commonly give sandstone concretions their rusty brown color and help bind quartz grains.
Field identification & locations
Look for a gritty texture and visible sand grains; a fresh scratch may expose grains that can scratch glass. Similar material occurs in sedimentary basins worldwide.
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