metamorphic
Quartzite river stone
Quartzite (SiO2 silicon dioxide)
Mohs hardness of 7, color ranges from grey to tan with dark banding, earthy to vitreous luster, granular micro-crystalline structure, smooth water-worn texture.
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Physical properties
Mohs hardness of 7, color ranges from grey to tan with dark banding, earthy to vitreous luster, granular micro-crystalline structure, smooth water-worn texture.
Formation & geological history
Formed when quartz-rich sandstone is subjected to heat and pressure (metamorphism). Usually found in riverbeds or coastal areas where erosion has rounded the specimen over long periods.
Uses & applications
Commonly used in landscaping, road construction as aggregate, and as decorative river rocks. High-purity quartzite is used to produce glass and metallic silicon.
Geological facts
Quartzite is extremely durable and weather-resistant; it is often harder than the steel blade of a knife. The banding seen in this specimen likely reflects the original sedimentary layers of the parent sandstone.
Field identification & locations
Identify in the field by its inability to be scratched by a steel nail and its grainy, sugary look on a fresh break. Common in glacial till and river basins across North America.
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