metamorphic
Quartzite River Rock
Quartzite ($SiO_2$)
Hardness: 7 (Mohs scale), Color: Brownish-grey with iron staining, Luster: Dull to vitreous, Crystal structure: Granoblastic, Cleavage: None, Specific gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: Brownish-grey with iron staining, Luster: Dull to vitreous, Crystal structure: Granoblastic, Cleavage: None, Specific gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the individual sand grains to recrystallize. This specific specimen shows rounding typical of alluvial or river-worn environments.
Uses & applications
Commonly used in construction as crushed stone for road beds, landscaping, and as a durable decorative stone. High-purity quartzite is used to produce silica sand for industrial processes.
Geological facts
Quartzite is so tough that it usually breaks through the quartz grains rather than along the boundaries between them, unlike its parent rock, sandstone. It is one of the most durable rocks on the Earth's surface.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass) and its grainy, sugary texture. Often found in riverbeds, glacial tills, and mountain ranges where ancient sedimentary layers have been metamorphosed.
