metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, brownish-orange, or off-white; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.63-2.65
- Hardness
- 7 on Mohs scale
- Color
- Tan, brownish-orange, or off-white
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, brownish-orange, or off-white; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.63-2.65
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure. The original quartz sand grains recrystallize into a dense, interlocking mosaic of quartz crystals.
Uses & applications
Used as a decorative stone in landscaping, as a crushed stone in road construction and railroad ballast, and sometimes in glass manufacturing if high purity.
Geological facts
Quartzite is so durable that it can survive intense weathering, often remaining as a caprock on mountains while 주변 rocks erode away. It is harder than a steel knife and will scratch glass.
Field identification & locations
Identify in the field by its extreme hardness and the fact that it breaks across grain boundaries rather than around them (unlike sandstone). Commonly found in folded mountain ranges.
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