metamorphic
Quartzite
Metamorphic Quartzite
Hardness: 7 on Mohs scale; Color: Brown, tan, pink, or gray; Luster: Vitreous to greasy; Crystal structure: Interlocking quartz grains; Cleavage: None (fractures conchoidally through grains); Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Brown, tan, pink, or gray
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 7 on Mohs scale; Color: Brown, tan, pink, or gray; Luster: Vitreous to greasy; Crystal structure: Interlocking quartz grains; Cleavage: None (fractures conchoidally through grains); Specific gravity: 2.65
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or chert under high tectonic heat and pressure, typically in mountain-building events over millions of years.
Uses & applications
Used in construction, as crushed stone for road bases, railway ballast, manufacturing of silica brick, and sometimes as decorative stone or countertops.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why quartz-rich sandstone parent rocks transform into ridges that resist erosion, forming prominent mountain peaks.
Field identification & locations
Identified by its high hardness (scratches glass easily), lack of effervescence with acid, and the sugary texture of interlocking quartz crystals visible under magnification. Common worldwide in ancient orogenic belts.
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