metamorphic
Quartzite
Quartzite (Metamorphic rock composed primarily of quartz)
Hardness of 7 on the Mohs scale, color typically white to gray (sometimes pink or red due to iron impurities), vitreous to greasy luster, non-foliated crystalline structure, and conchoidal fracture.
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Physical properties
Hardness of 7 on the Mohs scale, color typically white to gray (sometimes pink or red due to iron impurities), vitreous to greasy luster, non-foliated crystalline structure, and conchoidal fracture.
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure associated with tectonic compression, usually in mountain-building processes.
Uses & applications
Used in construction, railroad ballast, decorative aggregates, wall cladding, and sometimes in countertops and monuments.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why quartz-rich rocks often survive as pebbles and boulders long after other minerals have eroded away.
Field identification & locations
Can be identified by its inability to be scratched by steel, its lack of effervescence with acid, and the fused quartz grains visible under a hand lens. Commonly found globally in ancient mountain belts.
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