metamorphic
Quartzite Pebble
Quartzite (mostly SiO2)
Hardness: 7 (Mohs scale), Color: light grey to tan, Luster: dull to vitreous when polished, Crystal structure: granular/non-foliated, Cleavage: none (conchoidal fracture).
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Physical properties
Hardness: 7 (Mohs scale), Color: light grey to tan, Luster: dull to vitreous when polished, Crystal structure: granular/non-foliated, Cleavage: none (conchoidal fracture).
Formation & geological history
Forms through the metamorphism of quartz-rich sandstone under intense heat and pressure. This specific specimen has been further shaped by fluvial or glacial erosion into a rounded pebble.
Uses & applications
Used in construction as road ballast, in glass manufacturing, as a decorative garden stone, and as an abrasive in some industrial processes.
Geological facts
Quartzite is so tough that it often outlasts the softer rocks around it, leading to its prevalence as stream pebbles. It is one of the most chemically and physically resistant rocks found on Earth's surface.
Field identification & locations
Identify in the field by its inability to be scratched by steel and its grainy, sugary texture under a lens. It appears in riverbeds, beaches, and glaciated regions globally.
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