metamorphic
Red Quartzite
Quartzite (Metamorphic quartz sandstone)
Hardness of 7 on the Mohs scale, reddish-brown to dark red color due to iron oxide impurities, vitreous to greasy luster, massive crystal structure with interlocking quartz grains, conchoidal fracture with no true cleavage, and a specific gravity around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, reddish-brown to dark red color due to iron oxide impurities, vitreous to greasy luster, massive crystal structure with interlocking quartz grains, conchoidal fracture with no true cleavage, and a specific gravity around 2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and tectonic pressure, typically during mountain-building events (orogenic belts) over millions of years.
Uses & applications
Used in construction as crushed stone for road bases, railroad ballast, decorative landscaping, building stone, and occasionally for high-purity silica in manufacturing.
Geological facts
Quartzite is extremely resistant to weathering and chemical erosion, which is why ancient mountain ranges often weather down to ridges made primarily of quartzite.
Field identification & locations
Can be identified in the field by its high hardness (it will easily scratch glass and cannot be scratched by a knife) and the sugary, interlocking crystalline texture visible on fractured surfaces. Found globally where ancient sandstones underwent regional metamorphism.
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