metamorphic
Quartzite
Quartzite (Metamorphic Quartz Sandstone)
Hardness: 7 on the Mohs scale; Color: Typically white to gray, but can be pink, red, or yellow due to iron impurities; Luster: Vitreous to greasy on fresh surfaces; Crystal structure: Interlocking quartz crystals; Cleavage: None (fractures conchoidally); Specific gravity: 2.65
- Hardness
- 7 on the Mohs scale
- Luster
- Vitreous to greasy on fresh surfaces
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Physical properties
Hardness: 7 on the Mohs scale; Color: Typically white to gray, but can be pink, red, or yellow due to iron impurities; Luster: Vitreous to greasy on fresh surfaces; Crystal structure: Interlocking quartz crystals; Cleavage: None (fractures conchoidally); Specific gravity: 2.65
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically in tectonic mountain-building events over millions of years.
Uses & applications
Used in construction, as crushed stone for roadbeds, railway ballast, manufacturing of silica brick, and sometimes as a decorative dimension stone or in countertops.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why mountains made of quartzite often remain as prominent ridges long after surrounding rock has eroded.
Field identification & locations
Identified in the field by its extreme hardness (scratches glass easily, cannot be scratched by a knife) and the sugary texture of interlocking quartz grains on fractured surfaces. Common worldwide.
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