metamorphic
Quartzite
Quartzite (composed primarily of SiO2)
Hardness: 7 (Mohs scale), Color: pinkish-orange to grey with translucent grains, Luster: Vitreous/Glassy, Crystal Structure: Granular/Crystalline, Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: pinkish-orange to grey with translucent grains, Luster: Vitreous/Glassy, Crystal Structure: Granular/Crystalline, Specific Gravity: 2.6-2.7
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure during regional metamorphism, causing the quartz grains to recrystallize and fuse together.
Uses & applications
Used in construction as a decorative stone, road ballast, and railroad beds. Also used for high-end countertops and as a source of silica for glass manufacturing.
Geological facts
Quartzite is so hard and durable that it often forms the crests of ridges and hills, as it resists erosion much better than surrounding softer rocks. It will scratch glass easily.
Field identification & locations
Identify by its hardness (7), sugary granular texture, and lack of reaction to acid. It is commonly found in mountainous regions or ancient shield areas like the Appalachians or Scandinavia.
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