metamorphic

Weathered quartz-rich cobble, likely quartzite

Quartzite (mostly microcrystalline SiO₂), possibly quartz-rich sandstone or vein quartz

AI-generated identification · may be incorrect

Hardness about 7 Mohs; opaque cream, honey-yellow to brown surface with white quartz patches, vitreous to dull luster, massive granular texture, and no obvious cleavage. The yellow-brown coloration likely comes from iron-oxide staining and weathering.

Identified September 6, 2026More metamorphic →

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Physical properties

Formation & geological history

Quartzite forms when quartz sandstone is recrystallized under heat and pressure during metamorphism; the specimen’s exact age and source cannot be determined from the image. It may also be weathered vein quartz or silicified sandstone.

Uses & applications

Used as crushed stone, aggregate, road material, building stone, and decorative rock; attractive pieces may be tumbled or collected. This ordinary cobble has minimal commercial value.

Geological facts

Quartzite commonly preserves interlocking quartz grains and breaks across grains rather than around them, producing a very hard, durable surface.

Field identification & locations

Common in metamorphic terrains and river gravels worldwide, including the Appalachians, Rocky Mountains, and many shield regions. A steel nail should not scratch it; acid typically produces no reaction, helping distinguish it from limestone.