metamorphic
Quartzite (or Ferruginous Quartz)
Silicon Dioxide (SiO2) with Iron Oxide inclusions
Hardness: 7 (Mohs scale), Color: Pinkish-brown or tan due to iron staining, Luster: Vitreous to waxy, Crystal Structure: Hexagonal (microcrystalline), Cleavage: None/Conchoidal fracture
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Physical properties
Hardness: 7 (Mohs scale), Color: Pinkish-brown or tan due to iron staining, Luster: Vitreous to waxy, Crystal Structure: Hexagonal (microcrystalline), Cleavage: None/Conchoidal fracture
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone. High heat and pressure Recrystallize the sand grains into a dense, interlocking matrix. This specimen likely weathered out of a formation and became rounded through water action.
Uses & applications
Used in construction as crushed stone or decorative gravel, as a source for silica in glass making, and by lapidaries for tumbling or cabochons.
Geological facts
Quartzite is so tough that it often survives intense weathering that destroys other rocks. It is harder than a steel knife and will scratch glass easily.
Field identification & locations
Identify in the field by its grainy texture (sparkling under light) but extreme hardness. It won't react to acid like limestone. Common in mountain ranges and river beds.
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