metamorphic
Quartzite
Quartzite (composed primarily of SiO2)
Hardness: 7 (Mohs scale), Color: Creamy white to pale yellow, Luster: Vitreous to greasy, Crystal structure: Hexagonal (microcrystalline/granoblastic), Cleavage: None (conchoidal to irregular fracture)
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Physical properties
Hardness: 7 (Mohs scale), Color: Creamy white to pale yellow, Luster: Vitreous to greasy, Crystal structure: Hexagonal (microcrystalline/granoblastic), Cleavage: None (conchoidal to irregular fracture)
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, causing the original quartz grains to recrystallize and fuse together into a dense, hard rock.
Uses & applications
Used as a decorative stone in landscaping, crushed for road construction ballast, and high-purity varieties are used to produce silica sand for glassmaking and industrial applications.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks in a landscape, forming prominent ridges and hills. It is often confused with marble but can be distinguished by its superior hardness.
Field identification & locations
Identified in the field by its grainy, sandpaper-like texture that cannot be scratched by a steel nail. This specific specimen shows characteristic sugary texture and translucent edges. Common in mountain ranges and ancient shield areas globally.
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