metamorphic
Quartzite Pebble
Quartzite (primarily SiO2)
Hardness: 7 (Mohs), Color: Light gray, tan, or white with iron staining, Luster: Vitreous to dull, Structure: Granular/crystalline, Cleavage: None/conchoidal fracture, Specific gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs), Color: Light gray, tan, or white with iron staining, Luster: Vitreous to dull, Structure: Granular/crystalline, Cleavage: None/conchoidal fracture, Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, typically in orogenic (mountain-building) zones. It often undergoes secondary erosion and smoothing in river or coastal environments.
Uses & applications
Commonly used as crushed stone for road construction, railway ballast, and in some decorative landscaping due to its extreme durability. Highly pure quartzite is used to produce glass and silicon metal.
Geological facts
Quartzite is so tough that it often survives intense weathering better than surrounding rocks, frequently making up the tops of mountain ranges or appearing as rounded durable pebbles in riverbeds.
Field identification & locations
Identify in the field by its inability to be scratched by steel and its tendency to break through the quartz grains rather than around them. Found globally, especially in old metamorphic shields.
