metamorphic
Quartzite with Chlorite
Metamosphosed Quartz Sandstone (SiO2 with (Mg,Fe)3(Si,Al)4O10(OH)2 inclusions)
Hardness: 7 on Mohs scale; Color: White to light green/grey; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- White to light green/grey
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: White to light green/grey; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together, while the green tint suggests the presence of chlorite minerals formed during low-grade metamorphism.
Uses & applications
Used in construction as crushed stone or road ballast, as decorative stone in landscaping, or as a source of silica in glass manufacturing.
Geological facts
Quartzite is so tough that it often breaks through the individual quartz grains rather than around them, which distinguishes it from sandstone. The green hue often indicates it was formed in a 'greenschist' metamorphic facies environment.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass and steel) and its granular, sugary texture. Common in ancient mountain belts and shield areas like the Appalachians or the Canadian Shield.
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