metamorphic
Quartzite
Recrystallized Silicon Dioxide (SiO2)
Mohs hardness of 7, color ranging from orange-tan to rusty brown due to iron oxides, vitreous to dull luster, granoblastic texture with interlocking quartz grains.
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Physical properties
Mohs hardness of 7, color ranging from orange-tan to rusty brown due to iron oxides, vitreous to dull luster, granoblastic texture with interlocking quartz grains.
Formation & geological history
Formed when quartz-rich sandstone is subjected to intense heat and pressure during regional metamorphism, causing quartz grains to fuse together.
Uses & applications
Used in construction as road ballast, decorative stone for landscaping, and occasionally in glassmaking if high in purity.
Geological facts
Quartzite is so hard and durable that it often forms the resistant ridges and hilltops of old mountain ranges. It is harder than steel and can scratch glass easily.
Field identification & locations
Identify in the field by its sugary texture and extreme hardness. Unlike many sedimentary rocks, it will break through the grains rather than around them. Found globally in ancient mountain belts.
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