metamorphic
Quartzite Cobble (Iron-stained)
Quartzite (SiO2)
Hardness: 7 on Mohs scale. Color: Tan, orange-brown, reddish-yellow due to iron oxide staining, with lighter interior quartz core. Luster: Vitreous to waxy/dull weathered surface. Structure: Granoblastic, non-foliated. Cleavage: None, fractures conchoidally to irregularly.
- Hardness
- 7 on Mohs scale
- Luster
- Vitreous to waxy/dull weathered surface
Identified More metamorphic →
Explore Quartzite Cobble (Iron-stained) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 on Mohs scale. Color: Tan, orange-brown, reddish-yellow due to iron oxide staining, with lighter interior quartz core. Luster: Vitreous to waxy/dull weathered surface. Structure: Granoblastic, non-foliated. Cleavage: None, fractures conchoidally to irregularly.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone under extreme heat and pressure, fusing quartz grains together into a dense, hard rock. The rounded shape indicates extensive transportation by water in a stream or river bed.
Uses & applications
Used as aggregate in construction, road base, landscaping rock, and decorative river cobble.
Geological facts
Quartzite is extremely resistant to chemical and physical weathering. Often, iron oxide (hematite or limonite) carried by groundwater stains the outer shell of river-worn quartzite cobbles a distinct yellowish-orange or reddish color.
Field identification & locations
Look for a smooth, stream-rounded surface with iron staining that, if chipped, reveals a hard, sugary glass-like quartz texture inside. Commonly found in riverbeds, glacial tills, and alluvial deposits worldwide.
More like this
