metamorphic
Quartzite
Quartzite (SiO2-rich metamorphic rock)
Hardness 7 on Mohs scale, color ranges from light grey to white or light yellow, dull to vitreous luster, non-foliated granoblastic texture, very durable and weather-resistant
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Physical properties
Hardness 7 on Mohs scale, color ranges from light grey to white or light yellow, dull to vitreous luster, non-foliated granoblastic texture, very durable and weather-resistant
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure during regional metamorphism, causing quartz grains to recrystallize and interlock tightly
Uses & applications
Used in construction as crushed stone for road base and railroad ballast, decorative landscape stone, flagstone for paving, and dimension stone for building facings
Geological facts
Quartzite is extremely hard and resistant to chemical weathering; unlike sandstone which fractures around grain boundaries, quartzite breaks directly through the quartz grains
Field identification & locations
Look for a sugary, crystalline appearance on fresh surfaces and extreme hardness that easily scratches glass; commonly found in mountainous regions, ancient shield areas, and stream gravels
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