metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on the Mohs scale. Color: White to light grey or pale brownish-white with sugary texture. Luster: Vitreous to greasy. Crystal Structure: Trigonal (interlocking quartz grains). Specific gravity: 2.6-2.7.
- Hardness
- 7 on the Mohs scale
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 7 on the Mohs scale. Color: White to light grey or pale brownish-white with sugary texture. Luster: Vitreous to greasy. Crystal Structure: Trigonal (interlocking quartz grains). Specific gravity: 2.6-2.7.
Formation & geological history
Formed through regional or contact metamorphism of quartz-rich sandstone under intense heat and pressure, recrystallizing quartz grains into an interlocking mosaic.
Uses & applications
Used as a dimension stone, crushed stone for construction, railroad ballast, quartz source for silicon production, and decor/landscaping.
Geological facts
Unlike sandstone, quartzite breaks across its constituent quartz grains rather than along grain boundaries, resulting in a smooth, glassy fracture surface.
Field identification & locations
Identified by its sugary, crystalline texture and extreme hardness (scratches glass easily). Commonly found in mountainous fold belts and Precambrian shield regions worldwide.
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