metamorphic
Rounded quartz-rich cobble, likely quartzite
Quartzite (mostly SiO₂); exact identification requires closer examination
AI-generated identification · may be incorrectTan to brown, granular, and rounded by abrasion; quartzite is typically Mohs 7, with a vitreous-to-dull luster and interlocking quartz grains. No obvious cleavage is visible.
Identified More metamorphic →
Explore Rounded quartz-rich cobble, likely quartzite in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Tan to brown, granular, and rounded by abrasion; quartzite is typically Mohs 7, with a vitreous-to-dull luster and interlocking quartz grains. No obvious cleavage is visible.
Formation & geological history
If quartzite, it formed when quartz-rich sandstone was metamorphosed and recrystallized under heat and pressure; its age cannot be determined from the image. The cobble was later rounded during transport by water or ice.
Uses & applications
Quartzite is used as crushed aggregate, paving and building stone, and occasionally as a decorative material; this cobble is mainly of modest collecting interest.
Geological facts
A useful clue for quartzite is that it tends to fracture through quartz grains rather than separating cleanly around them, unlike many sandstones.
Field identification & locations
The rounded shape suggests transport in a stream, shoreline, or glacial deposit. Similar quartz-rich cobbles occur widely; inspect a fresh break for fused, interlocking grains to distinguish quartzite from sandstone or other rocks.
More like this
