metamorphic
Quartz-rich metamorphic rock, likely quartzite
Quartzite; predominantly quartz (SiO₂), with minor feldspar, mica, and iron-oxide staining
AI-generated identification · may be incorrectTypically 7 Mohs, granular and very hard, with white-gray to pink-brown coloration and a glassy to sugary luster; quartz grains are tightly recrystallized and lack prominent cleavage, breaking irregularly.
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Physical properties
Typically 7 Mohs, granular and very hard, with white-gray to pink-brown coloration and a glassy to sugary luster; quartz grains are tightly recrystallized and lack prominent cleavage, breaking irregularly.
Formation & geological history
Forms when quartz-rich sandstone is buried and metamorphosed under heat and pressure, commonly during mountain building; its exact age depends on the source sandstone and metamorphic event.
Uses & applications
Used as crushed stone, road aggregate, building stone, countertops, and decorative slabs; attractive pieces are collected but usually have modest value.
Geological facts
Unlike sandstone, quartzite commonly fractures through individual grains rather than around them, making it exceptionally resistant to weathering.
Field identification & locations
Identify it by scratching glass, minimal porosity, and a grainy texture whose quartz grains appear fused; common in metamorphic mountain belts worldwide, including the Appalachians, Rockies, Alps, and India.
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