metamorphic
Quartzite (River Cobble)
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Tan to yellowish-brown due to iron staining; Luster: Dull to slightly waxy; Structure: Granitoid/Massive; Cleavage: None; SG: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan to yellowish-brown due to iron staining
- Luster
- Dull to slightly 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: Tan to yellowish-brown due to iron staining; Luster: Dull to slightly waxy; Structure: Granitoid/Massive; Cleavage: None; SG: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure. This specific rounded shape indicates it was later eroded and smoothed by high-energy water action in a river or glacial environment.
Uses & applications
Commonly used as crushed stone in construction, road ballast, or as decorative landscaping stones. Highly durable for outdoor use.
Geological facts
Quartzite is so hard that it can scratch glass and steel. It is one of the most resistant rocks to chemical and physical weathering, which is why it often survives as rounded cobbles in stream beds.
Field identification & locations
Identify in the field by its extreme hardness and grainy, 'sugary' texture when freshly broken. Found globally in old mountain belts and river basins.
More like this
