metamorphic
Quartzite
Metamorphosed Quartz Sandstone
Hardness of 7 on the Mohs scale, colors range from white and gray to pink, green, or yellow depending on impurities, vitreous to greasy luster, non-foliated crystal structure, conchoidal fracture with no distinct cleavage, specific gravity around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, colors range from white and gray to pink, green, or yellow depending on impurities, vitreous to greasy luster, non-foliated crystal structure, conchoidal fracture with no distinct cleavage, specific gravity around 2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and tectonic pressure, typically in mountain-building belts over millions of years.
Uses & applications
Used extensively in construction, road aggregate, railway ballast, manufacturing of silica brick, and sometimes as a decorative stone or dimension stone.
Geological facts
Quartzite is extremely durable and weather-resistant, often outlasting the mountains it forms. When weathered, it forms extremely resistant ridge lines.
Field identification & locations
Identified easily by its extreme hardness (scratches glass easily and cannot be scratched by a steel knife) and the way it breaks across quartz grains rather than around them. Found globally wherever ancient mountain ranges have eroded.
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