metamorphic
Quartzite
Quartzite (SiO2)
AI-generated identification · may be incorrectHardness: 7 on Mohs scale; Color: Gray, tan, and brown with waxy to dull luster; Structure: Granular/crystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.63-2.65
- Hardness
- 7 on Mohs scale
- Color
- Gray, tan, and brown with waxy to dull luster
Identified More metamorphic →
Explore Quartzite 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: Gray, tan, and brown with waxy to dull luster; Structure: Granular/crystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.63-2.65
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under high heat and pressure, typically in orogenic belts (mountain building zones). The original sand grains recrystallize into a dense network of interlocking quartz crystals.
Uses & applications
Used in construction as road ballast, railway ballast, and decorative stone. High-purity quartzite is used in glass making and metallurgy.
Geological facts
Quartzite is so tough that it often survives intense weathering better than other rocks. In the field, it is distinguished from sandstone because it fractures through the grains rather than around them.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and lack of reaction to acid. Commonly found in riverbeds as rounded 'river rocks' or cobbles due to its resistance to erosion.
More like this
