metamorphic
Quartzite
Quartzite (SiO2)
Mohs hardness of 7, vitreous to dull luster, granoblastic/massive texture, light pinkish-beige to tan color due to iron oxide staining, conchoidal to uneven fracture.
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Physical properties
Mohs hardness of 7, vitreous to dull luster, granoblastic/massive texture, light pinkish-beige to tan color due to iron oxide staining, conchoidal to uneven fracture.
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone under extreme heat and pressure, recrystallizing quartz grains into a dense interlocking matrix.
Uses & applications
Used as a dimension stone, crushed stone for construction and road base, railroad ballast, and decorative garden stone. High-purity specimens are used to source silicon for electronics.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering. It is so tough that when it breaks, it fractures through the quartz grains rather than around them, unlike its parent rock sandstone.
Field identification & locations
Identified by its extreme hardness (scratches glass easily) and sugary to glassy fused texture. Extremely common in ancient mountain belts, shield regions, and fluvial gravel deposits worldwide.
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