metamorphic
Quartzite
Quartzite (predominantly SiO2)
Hardness: 7 (Mohs scale); Color: White to light gray; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None, exhibits conchoidal fracture; Specific gravity: 2.6-2.7.
- Hardness
- 7 (Mohs scale)
- Color
- White to light gray
- Luster
- Vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 (Mohs scale); Color: White to light gray; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None, exhibits conchoidal fracture; Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. Under intense heat and pressure, original quartz grains recrystallize and fuse together. It can be found in mountain ranges or eroded riverbeds.
Uses & applications
Used in construction as crushed stone for road ballast, as decorative stone in landscaping (river rock), and historically for tool making due to its hardness.
Geological facts
Quartzite is so tough that it usually breaks through the quartz grains rather than around them, unlike sandstone. It is one of the most durable rocks on the Earth's surface.
Field identification & locations
Identify in the field by its extreme hardness (it will scratch glass easily) and grainy, sugary texture. Common in riverbeds and areas with ancient tectonic activity.
