metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: tan to creamy white, Luster: vitreous to dull, Crystal structure: Trigonal/Hexagonal system (microcrystalline), Cleavage: absent (conchoidal fracture), Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: tan to creamy white, Luster: vitreous to dull, Crystal structure: Trigonal/Hexagonal system (microcrystalline), Cleavage: absent (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz sandstone under high heat and pressure, causing recrystallization of quartz grains. Many specimens are found in Proterozoic or Paleozoic geological formations.
Uses & applications
Used as a decorative stone in landscaping, crushed stone for road construction, countertop materials, and occasionally as a source of high-purity silica for glassmaking.
Geological facts
Quartzite is so durable that it often remains as caps on mountain ridges after softer rocks have eroded away. It is significantly harder than the sandstone it originates from.
Field identification & locations
Identify by its ability to scratch glass and smooth, slightly waxy or sugary texture. This specimen is a river-rounded cobble, likely found in a fluvial or glacial deposit. Look for it in areas with ancient mountain belts.
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