metamorphic
River Quartzite (Water-worn Quartzite)
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale), Color: Brownish-orange to tan due to iron staining, Luster: Vitreous to dull, Crystal Structure: Hexagonal (microcrystalline), Cleavage: None/Conchoidal fracture, Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: Brownish-orange to tan due to iron staining, Luster: Vitreous to dull, Crystal Structure: Hexagonal (microcrystalline), Cleavage: None/Conchoidal fracture, Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz sandstone. High heat and pressure compressed the sand grains into a dense crystalline network. This specific specimen has been further shaped and smoothed by fluvial (river) erosion over thousands of years.
Uses & applications
Used primarily as construction aggregate, railway ballast, and decorative garden stone. Because of its hardness, it is also used in manufacturing glass and ceramics.
Geological facts
Quartzite is so hard that it will scratch glass easily. Many of these rounded stones found in riverbeds are extremely old, often dating back hundreds of millions of years, having survived intense weathering that breaks down softer rocks like limestone or shale.
Field identification & locations
Identify by its 'sugary' texture on fresh breaks and its extreme hardness; it cannot be scratched by a steel nail. This specimen shows a smooth, rounded surface typical of riverbed stones. Common in ancient glacial deposits and active river systems.
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