metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on the Mohs scale. Color: Off-white to tan/yellowish due to iron staining. Luster: Vitreous to dull. Texture: Granular, sugary appearance. Cleavage: None (breaks with conchoidal or irregular fracture).
- Hardness
- 7 on the Mohs scale
- Color
- Off-white to tan/yellowish due to iron staining
- Luster
- Vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on the Mohs scale. Color: Off-white to tan/yellowish due to iron staining. Luster: Vitreous to dull. Texture: Granular, sugary appearance. Cleavage: None (breaks with conchoidal or irregular fracture).
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together, creating an extremely hard and durable rock.
Uses & applications
Used in construction as road ballast, railway ballast, and crushed stone. High-purity quartzite is used to produce ferrosilicon and industrial silica sand. Also used for decorative landscaping.
Geological facts
Quartzite is so hard that it can scratch glass and steel. Unlike sandstone, which breaks around the grains, quartzite is so well-fused that it breaks through the individual quartz grains when struck.
Field identification & locations
Commonly found in mountain ranges or areas with ancient tectonic activity. Identify in the field by its hardness (will scratch a knife blade) and its granular 'sugary' texture on a fresh break.
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