metamorphic
Quartzite
Metamorphosed Quartz Sandstone
Hardness (Mohs scale): 7; Color: typically white to gray, but can be pink or yellow; Luster: vitreous to dull; Crystal structure: trigonal (microcrystalline); Cleavage: none; Specific gravity: 2.6–2.7
- Color
- typically white to gray, but can be pink or yellow
- Luster
- vitreous to dull
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Physical properties
Hardness (Mohs scale): 7; Color: typically white to gray, but can be pink or yellow; Luster: vitreous to dull; Crystal structure: trigonal (microcrystalline); Cleavage: none; Specific gravity: 2.6–2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone under extreme heat and pressure, causing the sand grains to recrystallize into a dense network of interlocking quartz crystals.
Uses & applications
Used primarily in construction for crushed stone in road base and railway ballast. Also used as decorative stone in architecture, countertops, and flooring.
Geological facts
Quartzite is so tough that it often fractures across the original sand grains rather than around them, a key distinction from its parent sandstone. It is resistant to chemical weathering and often forms prominent ridges.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by steel) and lack of reaction to acid. Often found in mountain belts or areas with ancient metamorphic basement rock.
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