metamorphic
Tumbled quartz-rich pebble (likely quartzite)
Quartzite; predominantly SiO₂ (quartz)
AI-generated identification · may be incorrectHardness about 7 Mohs; rounded, pale tan to cream with a matte, fine-grained surface and a small reddish-brown iron-oxide stain. Quartz has a trigonal crystal structure, no cleavage, conchoidal fracture, and specific gravity near 2.65.
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Physical properties
Hardness about 7 Mohs; rounded, pale tan to cream with a matte, fine-grained surface and a small reddish-brown iron-oxide stain. Quartz has a trigonal crystal structure, no cleavage, conchoidal fracture, and specific gravity near 2.65.
Formation & geological history
Quartzite forms when quartz-rich sandstone is recrystallized under heat and pressure during metamorphism; its exact geological age cannot be determined from the photograph. The smooth spherical shape indicates natural stream abrasion or tumbling.
Uses & applications
Used as aggregate, paving and building stone; attractive pieces are sold as tumbled stones or craft materials, though this specimen has little gem value.
Geological facts
Quartzite commonly resembles chert, quartz, or pale sandstone but is notably hard and scratches ordinary glass. Iron oxides produce the reddish discoloration.
Field identification & locations
Common in metamorphic mountain belts and river gravels worldwide. Confirm by attempting to scratch glass and checking for a sugary, interlocking quartz texture; it should not fizz in dilute acid.
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