metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: White to light gray, Luster: Vitreous to dull, Crystal Structure: Trigonal (granular), Cleavage: None/Conchoidal fracture, Specific Gravity: 2.6-2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: White to light gray, Luster: Vitreous to dull, Crystal Structure: Trigonal (granular), Cleavage: None/Conchoidal fracture, Specific Gravity: 2.6-2.65
Formation & geological history
Formed from the metamorphism of quartz sandstone under intense heat and pressure, typically during mountain-building events. Geological age varies by deposit.
Uses & applications
Used in construction as crushed stone, railway ballast, decorative stone in landscaping, and sometimes in the manufacturing of glass and ceramics.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the caps of ridges and mountains because it resists erosion better than surrounding rocks.
Field identification & locations
Identified in the field by its hardness (it scratches glass), its sugary or granular texture, and its lack of reaction to acid. Common globally in metamorphic belts.
