Quartzite pebble

Hardness: 7 (Mohs scale), Color: tan to yellowish-brown, Luster: dull to vitreous, Structure: granular interlocking quartz grains, Cleavage: none (conchoidal fracture).

Formed from the metamorphism of quartz-rich sandstone. Extreme heat and pressure cause the sand grains to recrystallize into a dense, hard metamorphic rock. Often weathered and rounded by water transport.

Commonly used as construction aggregate, road ballast, and decorative garden stone. Pure varieties are used in the production of glass and silicon.

Quartzite is so hard that it will scratch glass and even high-quality steel. When hit with a hammer, it typically breaks through the sand grains rather than around them, distinguishing it from sandstone.

Identify in the field by its hardness and granular texture. Look for it along riverbeds, beaches, and in glacial deposits. It is extremely resistant to chemical weathering.