metamorphic
Quartzite
Metamorphic Quartzite (primarily SiO2)
Hardness: 7 on the Mohs scale; Color: Typically white, gray, or pinkish; Luster: Vitreous to greasy; Crystal structure: Trigonal (microcrystalline interlocking quartz grains); Cleavage: None (fractures conchoidally); Specific gravity: 2.65.
- Hardness
- 7 on the Mohs scale
- Color
- Typically white, gray, or pinkish
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 7 on the Mohs scale; Color: Typically white, gray, or pinkish; Luster: Vitreous to greasy; Crystal structure: Trigonal (microcrystalline interlocking quartz grains); Cleavage: None (fractures conchoidally); Specific gravity: 2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or chert under high heat and pressure, typically in mountain-building events over millions of years.
Uses & applications
Used in construction, as road aggregate, railway ballast, manufacturing of silica brick, and occasionally for decorative landscaping or countertops.
Geological facts
Because quartz is extremely resistant to weathering, quartzite hills and ridges often stand out as prominent topographic features in landscapes.
Field identification & locations
Can be identified in the field by its extreme hardness (scratches glass easily, cannot be scratched by a knife) and the fact that it breaks across the quartz grains rather than around them, unlike sandstone.
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