metamorphic
Quartzite
Quartzite (mostly SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-white with dark inclusions; Luster: Vitreous to dull; Crystal structure: Non-foliated, interlocking quartz crystals; Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Grayish-white with dark inclusions
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-white with dark inclusions; Luster: Vitreous to dull; Crystal structure: Non-foliated, interlocking quartz crystals; Cleavage: None; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, causing quartz grains to recrystallize into a dense, interlocking mosaic.
Uses & applications
Used in construction for railway ballast, decorative stone in landscaping, flooring, and historically as a tool stone for lithics.
Geological facts
Quartzite is so tough that it usually breaks through the quartz grains rather than along their boundaries, unlike its parent stone, sandstone.
Field identification & locations
Identify by its extreme hardness (it will easily scratch glass) and its granular, sugary texture on fresh surfaces. Often found in mountain ranges or eroded riverbeds as resistant pebbles.
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