metamorphic
Quartzite River Rock
Metamorphic Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Brownish-grey with iron staining; Luster: Dull to waxy; Crystal structure: Non-foliated, granular; Cleavage: None (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- Brownish-grey with iron staining
- Luster
- Dull to waxy
Identified More metamorphic →
Identify your own rocks.
Get a report just like this from any photo, free.
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.
More like this
