metamorphic
Quartzite River Rock
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: Red-brown to purple due to iron oxide, Luster: Dull to waxy, Crystal Structure: Trigonal (granular), Cleavage: None, Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: Red-brown to purple due to iron oxide, Luster: Dull to waxy, Crystal Structure: Trigonal (granular), Cleavage: None, Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz sandstone under high heat and pressure. This specimen has been rounded and smoothed by water erosion (alluvial process) over thousands of years.
Uses & applications
Commonly used in landscaping, as railroad ballast, or crushed for construction aggregate. High-purity quartzite is used to produce silica sand for glass making.
Geological facts
Quartzite is so tough that it often survives intense glacial and fluvial transport where other rocks would crumble. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify by its hardness (will scratch a knife blade) and granular 'sugary' texture. Commonly found in riverbeds, glacial tills, and ancient mountain belts.
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