metamorphic
Quartzite River Rock
Metamorphosed Sandstone (SiO2)
Hardness: 7 (Mohs scale); Color: Tan, brown, or brownish-yellow due to iron staining; Luster: Dull to waxy; Crystal structure: Non-foliated, granular; Cleavage: None/Conchoidal fracture; Specific Gravity: 2.6-2.7.
- Hardness
- 7 (Mohs scale)
- Color
- Tan, brown, or brownish-yellow due to iron staining
- Luster
- Dull to waxy
Identified More metamorphic →
Explore Quartzite River Rock in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs scale); Color: Tan, brown, or brownish-yellow due to iron staining; Luster: Dull to waxy; Crystal structure: Non-foliated, granular; Cleavage: None/Conchoidal fracture; Specific Gravity: 2.6-2.7.
Formation & geological history
Formed when quartz-rich sandstone is subjected to intense heat and pressure, causing the original quartz grains to recrystallize. This specific piece is a water-worn river cobble, rounded by abrasive action in a fluvial environment.
Uses & applications
Commonly used as crushed stone in road construction, railway ballast, and decorative landscaping. High-purity quartzite is used in glassmaking and metallurgy.
Geological facts
Quartzite is so tough that it often breaks through the constituent quartz grains rather than along their boundaries. It is more resistant to erosion than most other rocks, often forming the caps of hills and mountains.
Field identification & locations
Identify in the field by its hardness (it will easily scratch glass) and lack of reaction to acid. Look for it in riverbeds, glacial tills, or mountain outcrops. It feels denser and smoother than sandstone.
More like this
