Quartzite cobble

Hardness 7 on Mohs scale; color ranges from tan and yellow-brown to gray due to iron staining; dull to slightly vitreous luster; granular texture; extremely durable and resistant to scratching.

Formed from the metamorphism of quartz sandstone under intense heat and pressure, often during mountain-building events. These specific rounded shapes are created through long-term water erosion in riverbeds or glacial transport.

Used primarily as crushed stone for road construction, railroad ballast, and as decorative landscaping rock. Sometimes used in glassmaking or as a building material.

Quartzite is one of the most physically durable and chemically resistant rocks found on Earth's surface. It is often harder than the steel tools used to mine it.

Identify by its ability to easily scratch glass and its lack of reaction to acid. Look for rounded, smooth edges from water wear and a dense, sugary or crystalline texture on fresh breaks.