metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 (Mohs), Color: White to grayish with tan iron staining, Luster: Vitreous to dull when water-worn, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs), Color: White to grayish with tan iron staining, Luster: Vitreous to dull when water-worn, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone under extreme heat and pressure, causing recrystallization of quartz grains. These rounded pebbles are typically the result of fluvial erosion (found in riverbeds) or coastal wave action.
Uses & applications
Commonly used as high-quality aggregate in construction, as decorative landscaping stone, and as a raw material for glass and ceramic manufacturing.
Geological facts
Quartzite is so dense and tough that when it breaks, it fractures through the quartz grains rather than along the boundaries between them, unlike its parent rock sandstone.
Field identification & locations
Identify in the field by its superior hardness (cannot be scratched by steel) and lack of reaction to acid. It is commonly found in gravel pits and beaches worldwide.
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