metamorphic
Quartzite
Metamorphic Quartzite (primarily SiO2)
Hardness: 7 on the Mohs scale. Color: Generally white to gray, but can be pink, red, or yellow due to iron oxide impurities. Luster: Vitreous to greasy on fresh surfaces. Crystal structure: Non-foliated, interlocking quartz crystals. Cleavage: None (fractures conchoidally through the grains rather than around them).…
- Hardness
- 7 on the Mohs scale
- Luster
- Vitreous to greasy on fresh surfaces
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Physical properties
Hardness: 7 on the Mohs scale. Color: Generally white to gray, but can be pink, red, or yellow due to iron oxide impurities. Luster: Vitreous to greasy on fresh surfaces. Crystal structure: Non-foliated, interlocking quartz crystals. Cleavage: None (fractures conchoidally through the grains rather than around them). Specific gravity: 2.60 to 2.80.
Formation & geological history
Formed from quartz-rich sandstone or chert under high temperature and pressure associated with regional metamorphism. Geological age varies widely depending on the formation site, ranging from Precambrian to Cenozoic.
Uses & applications
Used as crushed stone in construction, road aggregate, railroad ballast, manufacturing of silica bricks, and occasionally as decorative stone or countertops.
Geological facts
Because quartz is extremely resistant to weathering, quartzite hills and ridges often stand out as prominent resistant landforms in the landscape. It is so durable that sandstone completely transforms into quartzite without any remaining pore space.
Field identification & locations
Can be identified in the field by its extreme hardness (scratches glass easily and cannot be scratched by a knife) and the way it fractures across individual quartz grains rather than splitting around them like sandstone. Found worldwide in mountainous and ancient cratonic regions.
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