metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-white with some iron staining; Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None (conchoidal to irregular fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Grayish-white with some iron staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-white with some iron staining; Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None (conchoidal to irregular fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. Under intense heat and pressure, quartz grains recrystallize and fuse together. This specimen appears to be from a Precambrian or Paleozoic formation.
Uses & applications
Used in construction as crushed stone for road ballast, as a decorative stone in landscaping, and historically for stone tools due to its hardness and sharp edges.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, frequently forming the peaks of ridges and mountains. It is harder than a steel knife and will easily scratch glass.
Field identification & locations
Identify in the field by its sugary, granular texture and its inability to be scratched by a steel blade. It differs from sandstone because it breaks through the quartz grains rather than around them. Common in mountain ranges globally.
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