metamorphic
Quartzite Pebble
Quartzite
Hardness of 7 on the Mohs scale, colors ranging from pink, purple, and brown due to iron oxide impurities, vitreous to greasy luster, massive crystal structure with interlocking quartz grains, conchoidal fracture, specific gravity around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, colors ranging from pink, purple, and brown due to iron oxide impurities, vitreous to greasy luster, massive crystal structure with interlocking quartz grains, conchoidal fracture, specific gravity around 2.65.
Formation & geological history
Formed from quartz-rich sandstone or chert that has been subjected to intense heat and pressure (regional or contact metamorphism), causing quartz grains to recrystallize.
Uses & applications
Used in construction, road aggregate, railway ballast, and occasionally as decorative landscaping stones or tumbled stones.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why it often survives as smooth pebbles on beaches and in riverbeds long after softer rocks have eroded away.
Field identification & locations
Identified by its high hardness (scratches glass), lack of fizz with acid, and the sugary texture of interlocking quartz crystals visible on fresh breaks. Found globally in ancient mountain belts.
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