metamorphic
Quartzite
Quartzite (SiO2-rich metamorphic rock)
Hardness: 7 on Mohs scale; Color: typically white, gray, or brown from impurities; Luster: vitreous (glassy) to dull; Crystal structure: Trigonal/Hexagonal system in granular form; Cleavage: none; Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or brown from impurities
- Luster
- vitreous (glassy) to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or brown from impurities; Luster: vitreous (glassy) to dull; Crystal structure: Trigonal/Hexagonal system in granular form; Cleavage: none; Specific gravity: 2.6-2.7.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone. High heat and pressure reciprocal to tectonic compression cause quartz grains to recrystallize and fuse together.
Uses & applications
Used in construction as crushed stone or road ballast, as a building stone for walls and floors, and in the production of glass and silicon due to high silica content.
Geological facts
Quartzite is so tough that it often breaks through the individual quartz grains rather than around them, which is a key distinction from its parent sandstone.
Field identification & locations
Found globally in mountain ranges and areas with ancient continental crust. Identify by its high hardness (scratches glass) and sugary, crystalline texture that does not fizz with acid.
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