metamorphic
Quartzite
Metamorphic Rock (composed primarily of Quartz, SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or pinkish due to iron oxide; Luster: vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or pinkish due to iron oxide
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or pinkish due to iron oxide; Luster: vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. High heat and pressure cause the original quartz grains to recrystallize and fuse together into a dense, hard interlocking mosaic. This occurs during mountain-building events.
Uses & applications
Used as a decorative stone in landscaping, crushed for road ballast, as a raw material for glass making (if high purity), and in construction as flooring or wall cladding.
Geological facts
Quartzite is so hard that it will scratch glass and even high-quality steel. In natural landscapes, quartzite typically forms ridges and peaks because it is much more resistant to weathering than the surrounding rock types.
Field identification & locations
Identify in the field by its extreme hardness and the fact that, unlike sandstone, it breaks across the constituent grains rather than around them. It is commonly found in ancient mountain ranges and beach deposits as water-worn pebbles.
