metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, often with reddish or brown iron staining; Luster: vitreous (glassy) to dull; Crystal structure: hexagonal patterns at microscopic levels; Cleavage: none (breaks with conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Luster
- vitreous (glassy) to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, often with reddish or brown iron staining; Luster: vitreous (glassy) to dull; Crystal structure: hexagonal patterns at microscopic levels; Cleavage: none (breaks with conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together, losing the original sedimentary texture. This process occurs during mountain-building events in various geological eras.
Uses & applications
Used widely in construction as crushed stone for road beds and railway ballast, as dimension stone for flooring or wall coverings, and in the manufacturing of glass and ceramics when highly pure.
Geological facts
Quartzite is so durable that it can survive intense weathering over millions of years, often forming the resistant ridges of mountain ranges. Unlike sandstone, when quartzite is broken, it fractures through the sand grains rather than around them.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by steel) and its granular, sugary appearance. It is commonly found in mountainous regions or stable continental interiors where ancient seabed sandstones have been buried and heated.
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