metamorphic
Quartzite
Quartzite (composed primarily of SiO2)
Hardness: 7 (Mohs scale), Color: Pinkish-red due to iron oxide impurities, Luster: Vitreous to dull, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6 - 2.7
Identified More metamorphic →
Explore Quartzite in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs scale), Color: Pinkish-red due to iron oxide impurities, Luster: Vitreous to dull, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6 - 2.7
Formation & geological history
Formed from the regional metamorphism of quartz-rich sandstone under intense heat and pressure, where quartz grains recrystallize and fuse together into a dense mass. Found in mountain-building belts worldwide.
Uses & applications
Used in construction as crushed stone or decorative facing stone, as a source of silica for glass manufacturing, and as a ballast for railways.
Geological facts
Quartzite is so tough that it often outlasts surrounding rocks in mountain ranges, remaining as the caps of mountains after other layers have eroded away. It is significantly harder than the sandstone it originates from.
Field identification & locations
Identified in the field by its inability to be scratched by steel, its sugary texture on broken surfaces, and its tendency to break across the quartz grains rather than around them. Common in the Appalachian Mountains and the Great Lakes region.
More like this
