metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale); Color: Gray, tan, brown, or white; Luster: Vitreous to dull/sugary; Structure: Granular, non-foliated; Cleavage: None (conchoidal fracture); SG: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Gray, tan, brown, or white
- Luster
- Vitreous to dull/sugary
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Physical properties
Hardness: 7 (Mohs scale); Color: Gray, tan, brown, or white; Luster: Vitreous to dull/sugary; Structure: Granular, non-foliated; Cleavage: None (conchoidal fracture); SG: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, typically during mountain-building events (orogeny). The original quartz sand grains recrystallize into a dense interlocking mosaic.
Uses & applications
Used in construction as crushed stone or building stone, in glass manufacturing if highly pure, and as decorative stone in landscaping or interior design.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the caps of ridges and mountains. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify by its hardness (scratches glass) and its granular, crystalline appearance that sparkles slightly in light. Found worldwide in ancient mountain belts like the Appalachians or Alps.
