metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale. Color: white, grey, or yellowish. Luster: vitreous to dull. Structure: granoblastic, non-foliated. Cleavage: none. Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- white, grey, or yellowish
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale. Color: white, grey, or yellowish. Luster: vitreous to dull. Structure: granoblastic, non-foliated. Cleavage: none. Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause quartz grains to recrystallize and fuse together, typically in orogenic (mountain-building) belts.
Uses & applications
Used in construction as crushed stone for road ballast, as decorative building stone, and historically for making stone tools due to its hardness and conchoidal fracture.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the ridges and peaks of mountain ranges because it weathers much slower than surrounding rocks.
Field identification & locations
Identify by its ability to scratch glass easily and its interlocking crystalline texture. Found globally in ancient mountain roots and shield areas like the Appalachians or the Scottish Highlands.
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