metamorphic
Quartzite
Quartzite (SiO2 silicon dioxide)
Hardness: 7 on Mohs scale; Color: typically white to gray, can be yellow or red; Luster: vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: none; Specific gravity: approx. 2.65.
- Hardness
- 7 on Mohs scale
- Color
- typically white to gray, can be yellow or red
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, can be yellow or red; Luster: vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: none; Specific gravity: approx. 2.65.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone. Under intense heat and pressure, quartz grains recrystallize and fuse together. The geological age varies wildly depending on the region of formation.
Uses & applications
Used extensively in the construction industry as road ballast, gravel, and dimension stone for flooring or countertops. Highly valued in high-purity forms for glassmaking and silicon production.
Geological facts
Quartzite is so durable that it can survive extreme weathering and is often found as resistant ridges on mountain tops. It is harder than steel and will scratch glass easily.
Field identification & locations
Identified in the field by its sugary texture, extreme hardness (scratches glass), and the way it breaks through the quartz grains rather than around them. Often found in areas of ancient mountain building.
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