metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, brown, or white with reddish staining; Luster: Vitreous to dull; Crystal structure: Non-foliated granoblastic; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan, brown, or white with reddish staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, brown, or white with reddish staining; Luster: Vitreous to dull; Crystal structure: Non-foliated granoblastic; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, typically during mountain-building events. The original quartz grains recrystallize and fuse into a dense rock.
Uses & applications
Used in construction as crushed stone or road ballast, as a high-quality building stone, and historically for stone tools due to its hardness and durability.
Geological facts
Quartzite is so hard that it can scratch glass and steel. It is often more resistant to weathering than the surrounding rock, often forming the crests of ridges and resistant hilltops.
Field identification & locations
Identify by its extreme hardness and sugary, crystalline texture where grains have fused. It will not fizz with acid. Common in ancient mountain belts like the Appalachians or the Alps.
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