metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: tan to light brown, Luster: Vitreous to dull, Crystal Structure: Hexagonal (microcrystalline), Cleavage: Indistinct/Conchoidal fracture, Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: tan to light brown, Luster: Vitreous to dull, Crystal Structure: Hexagonal (microcrystalline), Cleavage: Indistinct/Conchoidal fracture, Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure. Most commonly found in ancient mountain belts and shield areas dating back to the Proterozoic or Paleozoic eras.
Uses & applications
Used in construction as crushed stone, road ballast, and decorative stone. High-purity quartzite is used in glassmaking and as a source of silicon for semiconductors.
Geological facts
Quartzite is so durable that it often survives erosion better than the surrounding rocks, forming prominent ridges and hills. It is often confused with marble, but quartzite will scratch glass while marble will not.
Field identification & locations
Identify by its extreme hardness and grainy, sugary texture. It is ubiquitous in glaciated regions and riverbeds. Collectors look for unique colors or included minerals.
