metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale); Color: White, tan, or grey with dark mineral streaks; Luster: Vitreous to dull; Structure: Granoblastic, non-foliated; Cleavage: None (conchoidal fracture); SG: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- White, tan, or grey with dark mineral streaks
- Luster
- Vitreous to dull
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 (Mohs scale); Color: White, tan, or grey with dark mineral streaks; Luster: Vitreous to dull; Structure: Granoblastic, non-foliated; Cleavage: None (conchoidal fracture); SG: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under high heat and pressure. This specimen shows water-worn rounding, likely originating from a riverbed or coastal environment.
Uses & applications
Used in construction as road ballast, railway ballast, and decorative stone. Highly pure quartzite is used to produce silica for glassmaking and silicon industrial products.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock in mountain ranges, forming prominent ridges and peaks. It is distinguished from sandstone because it breaks through the grains rather than around them.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by a steel knife) and its grainy but fused texture. It is extremely common in ancient mountain belts and glacial till.
More like this
