metamorphic
Rounded reddish-brown pebble, likely iron-stained quartzite or chert
Quartzite (mostly SiO₂), possibly ferruginous chert
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; reddish-brown to gray, dull to subtly vitreous luster, very fine-grained and massive, with no obvious cleavage. The smooth shape results from water abrasion; iron oxides create the red-brown coloration.
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Physical properties
Hardness about 6.5–7 Mohs; reddish-brown to gray, dull to subtly vitreous luster, very fine-grained and massive, with no obvious cleavage. The smooth shape results from water abrasion; iron oxides create the red-brown coloration.
Formation & geological history
Quartzite forms when quartz-rich sandstone is recrystallized under heat and pressure during metamorphism; chert forms by chemical or biogenic silica deposition. The pebble was later weathered and rounded in a stream, beach, or glacial setting; its precise age cannot be determined visually.
Uses & applications
Used as durable aggregate, road stone, landscaping material, and occasionally as a lapidary or decorative stone. This ordinary pebble has little commercial value.
Geological facts
A scratch test with hardened steel may leave little or no mark if it is quartz-rich; quartzite commonly scratches glass. A streak test is usually white to pale gray despite the surface’s red color.
Field identification & locations
Common in quartz-rich metamorphic terrains and gravel deposits worldwide. Check for granular quartz texture, strong resistance to scratching, and lack of fizz with dilute hydrochloric acid; exact identification would require microscopy or chemical testing.
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