metamorphic
Quartzite
Quartzite (Silicon Dioxide, SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, but light yellow/tan due to impurities; Luster: vitrous (glassy) to dull; Crystal structure: Trigonal (granular texture); Cleavage: None (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Luster
- vitrous (glassy) to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, but light yellow/tan due to impurities; Luster: vitrous (glassy) to dull; Crystal structure: Trigonal (granular texture); Cleavage: None (conchoidal fracture).
Formation & geological history
Quartzite is formed through the metamorphism of quartz sandstone. High pressure and heat cause the individual quartz grains to recrystallize and fuse together, typically occurring during mountain-building events (orogeny).
Uses & applications
Used in construction as crushed stone for road beds, as dimension stone in architecture (slabs for countertops), and occasionally for decorative gravel or jewelry if it contains unique colors.
Geological facts
Unlike sandstone, which breaks around the grains, quartzite is so strongly fused that it breaks through the quartz grains themselves. It is one of the most durable rocks on Earth's surface.
Field identification & locations
Identified in the field by its extreme hardness (cannot be scratched by a steel nail) and its granular, sugary appearance. It is found globally in mountainous regions where ancient sedimentary basins were compressed.
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