metamorphic
Quartzite (Quartz sand or Chert)
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: White to grey/translucent, Luster: Vitreous to waxy, Structure: Granular/microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7.
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Physical properties
Hardness: 7 (Mohs scale), Color: White to grey/translucent, Luster: Vitreous to waxy, Structure: Granular/microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or through the deposition of microcrystalline silica in sedimentary basins. These specimens are often reworked in glacial or river gravel deposits.
Uses & applications
Used as aggregate in construction, road ballast, glass manufacturing (if pure silica), and as decorative landscaping gravel. Rough specimens are common in geological collections.
Geological facts
Quartzite is so hard that it will scratch glass and steel. It is one of the most durable and weather-resistant rocks found on the Earth's surface.
Field identification & locations
Identify in the field by its extreme hardness and glassy luster on broken surfaces. It often appears as rounded river pebbles or sharp structural fragments in gravel pits globally.
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