Quartzite River Rock

Physical Properties

Hardness: 7 on Mohs scale; Color: Brownish-grey with iron staining; Luster: Dull to waxy; Crystal structure: Non-foliated, granular; Cleavage: None (conchoidal fracture).

Formation & Geological History

Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events (orogeny). This specific specimen has been rounded by fluvial (river) erosion over thousands of years.

Uses & Applications

Used in landscaping, as industrial aggregate for construction (road base, concrete fillers), and occasionally for ballast. Smooth varieties are sometimes used in lapidary art.

Geological Facts

Quartzite is so hard that it will scratch glass and even high-quality steel. It is one of the most durable rocks on Earth's surface, often outlasting the mountains it once helped form.

Field Identification & Locations

Identify in the field by its extreme hardness and the way it breaks through quartz grains rather than around them. Often found in riverbeds or glacial tills. It feels denser and smoother than sandstone.

Identified on: 4/30/2026

Mode: Standard