metamorphic
Quartzite
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or pink; Luster: vitreous (glassy); Crystal structure: Trigonal/Hexagonal aggregates; Cleavage: none (conchoidal fracture); Specific gravity: 2.63 - 2.65
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or pink
- Luster
- vitreous (glassy)
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or pink; Luster: vitreous (glassy); Crystal structure: Trigonal/Hexagonal aggregates; Cleavage: none (conchoidal fracture); Specific gravity: 2.63 - 2.65
Formation & geological history
Formed via regional metamorphism of quartz-rich sandstone. High heat and pressure reciprocal to tectonic activity cause recrystallization of individual quartz grains into an interlocking mosaic. Found in ancient mountain belts and shields.
Uses & applications
Used extensively in the construction industry for crushed stone, road ballast, and roofing. Higher quality slabs are popular as countertop material (Engineered or Natural) and decorative cladding. Also used in glass making and metallurgy.
Geological facts
Quartzite is so durable that it can survive intense weathering to form the peaks of mountain ranges. It is often harder and more resistant than the granite or sandstone it sits next to. Pure quartzite is approximately 99% silica.
Field identification & locations
Identified in the field by its grainy, sugary texture and extreme hardness (will easily scratch glass and steel). It lacks the foliation of schist or gneiss. Found in abundance in the Appalachian Mountains, USA, and the Brazilian Highlands.
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