metamorphic
Green Quartzite
Quartzite (SiO2 with chromium-rich muscovite/fuchsite inclusions)
Hardness: 7 (Mohs scale), Color: Pale mint green to white, Luster: Vitreous to dull, Crystal structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: Pale mint green to white, Luster: Vitreous to dull, Crystal structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone. Under intense heat and pressure, the sand grains recrystallize into a dense, interlocking mosaic of quartz. The green tint is often provided by trace amounts of fuchsite (chromium mica).
Uses & applications
Used primarily as decorative stone, countertops, paving, and occasionally as a low-cost gemstone for beads and cabochons.
Geological facts
Quartzite is so durable that it often remains as ridges or peaks on mountains because it resists weathering better than the surrounding rocks. It is harder than a steel knife blade.
Field identification & locations
Identify by its ability to scratch glass and its granular, 'sugary' texture. Commonly found in folded mountain belts. Collectors should look for a lack of reaction to acid to distinguish it from marble.
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