metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: white, gray, buff, or pink; Luster: vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular texture); Cleavage: None (conchoidal or irregular fracture); Specific Gravity: 2.6 - 2.7
- Hardness
- 7 on Mohs scale
- Color
- white, gray, buff, or pink
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: white, gray, buff, or pink; Luster: vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular texture); Cleavage: None (conchoidal or irregular fracture); Specific Gravity: 2.6 - 2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together, obliterating the original sedimentary texture and fossils.
Uses & applications
Used in construction as crushed stone for roadbeds and railway ballast. High-quality slabs are used for countertops, flooring, and decorative wall cladding. Fine-grained varieties are used in glass-making.
Geological facts
Quartzite is so tough that it often survives intense glacial erosion and weathering. It is one of the most durable rocks on Earth, often forming high ridges and resistant hills.
Field identification & locations
To identify in the field, look for a rock that is extremely hard (scratches glass) and breaks through the quartz grains rather than around them (unlike sandstone). Commonly found in folded mountain belts like the Appalachians or the Alps.
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