metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan, with yellow/brown iron staining visible here; Luster: Vitreous to dull; Crystal structure: Trigonal (granular); Cleavage: None, breaks with conchoidal fracture.
- Hardness
- 7 on Mohs scale
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan, with yellow/brown iron staining visible here; Luster: Vitreous to dull; Crystal structure: Trigonal (granular); Cleavage: None, breaks with conchoidal fracture.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. Under intense heat and pressure, original quartz grains recrystallize and fuse together. Often found in mountain belts and areas of ancient shield rock.
Uses & applications
Used as crushed stone for road construction, railway ballast, and as a decorative stone in landscaping. High-quality slabs are used for kitchen countertops.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the resistant peaks of mountain ranges. It is significantly harder than the sandstone it originates from and will scratch glass easily.
Field identification & locations
Identify by its extreme hardness and granular, sugary appearance on fresh surfaces. It is commonly found in riverbeds as rounded cobbles due to its durability. Look for it in areas with a history of tectonic activity.
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