metamorphic
Green Quartzite
Quartzite (primarily SiO2 with chromium-rich mica/fuchsite impurities)
Hardness: 7 (Mohs scale), Color: Pale to medium green with white/gray mottling, Luster: Vitreous to dull, Crystal Structure: Trigonal (granular texture), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: Pale to medium green with white/gray mottling, Luster: Vitreous to dull, Crystal Structure: Trigonal (granular texture), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the high-pressure and high-temperature metamorphism of quartz-rich sandstone. As the sandstone is heated, quartz grains recrystallize and interlock. The green hue is typically caused by the inclusion of chromium-bearing minerals like fuchsite.
Uses & applications
Used primarily as decorative stone, countertops, landscaping rock, and occasionally in jewelry as a substitute for jade or aventurine. It is also used as a durable construction aggregate.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the peaks of mountain ranges because it weathers much more slowly than surrounding rocks. Unlike marble, it will not etch when exposed to acidic substances like lemon juice or vinegar.
Field identification & locations
Identify in the field by its grainy, sugary texture and extreme hardness (it will easily scratch glass and steel). Commonly found in folded mountain belts and ancient cratons worldwide, such as the Appalachians or the Brazilian Shield.
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