metamorphic
Weathered Quartzite Pebble (with mineral inclusions)
Metamorphic Quartzite (predominantly SiO2)
AI-generated identification · may be incorrectHardness 6.5 to 7 on Mohs scale; color is mottled off-white to grayish with dark chloritic or tourmaline/amphibole patches; dull to waxy luster on weathered surface; microcrystalline/granoblastic texture; no cleavage, irregular to sub-conchoidal fracture; density around 2.65 g/cm³.
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Physical properties
Hardness 6.5 to 7 on Mohs scale; color is mottled off-white to grayish with dark chloritic or tourmaline/amphibole patches; dull to waxy luster on weathered surface; microcrystalline/granoblastic texture; no cleavage, irregular to sub-conchoidal fracture; density around 2.65 g/cm³.
Formation & geological history
Formed via regional or contact metamorphism of quartz-rich sandstone under heat and pressure, recrystallizing quartz grains. Subsequently subjected to fluvial or coastal mechanical weathering and chemical leaching, producing rounded shapes and weathered rind with fractures.
Uses & applications
Commonly used in crushed stone, construction aggregates, railway ballast, and occasionally tumbled or collected for decorative landscape gardening.
Geological facts
Quartzite is so durable that it frequently outlasts surrounding rocks during weathering, often forming the resistant capstones of ridges, mountain ranges, and stream cobbles over hundreds of millions of years.
Field identification & locations
Identified in the field by its extreme hardness (scratches glass and steel), granular sugary texture when freshly fractured, and inability to react with dilute hydrochloric acid. Abundant along riverbeds, beaches, and glacial gravel deposits worldwide.
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