metamorphic
Rounded quartz-rich cobble, likely quartzite
Quartzite; predominantly microcrystalline quartz (SiO₂), possibly with minor iron-oxide staining
AI-generated identification · may be incorrectHardness about 7 Mohs; gray-brown to mauve color, weathered matte-to-slightly silky luster, massive granular texture, and no obvious cleavage. Its rounded shape and smooth surface indicate stream or beach abrasion rather than crystal form.
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
Hardness about 7 Mohs; gray-brown to mauve color, weathered matte-to-slightly silky luster, massive granular texture, and no obvious cleavage. Its rounded shape and smooth surface indicate stream or beach abrasion rather than crystal form.
Formation & geological history
Quartzite forms when quartz-rich sandstone is recrystallized under heat and pressure during regional metamorphism; its age depends on the source formation and cannot be determined from the image. It commonly survives erosion as resistant cobbles.
Uses & applications
Used as crushed stone, aggregate, road material, building stone, countertops, and decorative landscaping rock; attractive pieces may be collected or polished.
Geological facts
Quartzite is generally harder and more resistant to weathering than sandstone. The mauve tint may result from iron oxides or minor accessory minerals.
Field identification & locations
Identify it by testing for quartz-like hardness: it should scratch ordinary glass, lack visible sand grains or bedding, and show interlocking grains on a fresh break. Common in metamorphic mountain belts and gravel deposits.
More like this
