metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, color ranges from white and grey to pink, red, or brown due to iron oxide impurities, vitreous to greasy luster, non-foliated crystal structure with interlocking quartz grains, specific gravity of 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, color ranges from white and grey to pink, red, or brown due to iron oxide impurities, vitreous to greasy luster, non-foliated crystal structure with interlocking quartz grains, specific gravity of 2.65.
Formation & geological history
Formed when quartz-rich sandstone or chert is subjected to high heat and pressure, typically through tectonic compression in orogenic belts. Geological age can range from Precambrian to Cenozoic.
Uses & applications
Used in construction, railroad ballast, crushed stone for road aggregates, manufacture of silica bricks, and occasionally as an ornamental stone or in decorative landscaping.
Geological facts
Unlike sandstone, quartzite breaks across the quartz grains rather than around them, demonstrating the extreme thermal and pressure conditions of its formation.
Field identification & locations
Identified by its hard, non-foliated texture, inability to be scratched by a steel knife, and the way it fractures through quartz grains rather than splitting along cementing material. Common worldwide in mountain ranges.
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