metamorphic
Quartzite
SiO2 (Silicon Dioxide)
Hardness: 7 (Mohs scale), Color: tan, yellow, orange (due to iron oxide staining), Luster: Vitreous to dull, Crystal Structure: Hexagonal (microcrystalline), Cleavage: Indistinct/Conchoidal fracture
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Physical properties
Hardness: 7 (Mohs scale), Color: tan, yellow, orange (due to iron oxide staining), Luster: Vitreous to dull, Crystal Structure: Hexagonal (microcrystalline), Cleavage: Indistinct/Conchoidal fracture
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause quartz grains to recrystallize and fuse together into a dense, hard rock. Typically found in mountain belts and Precambrian shields.
Uses & applications
Used as crushed stone for road construction, railway ballast, and as a decorative stone in landscaping. High-purity quartzite is used to produce glass and metallurgical-grade silicon.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, often forming the crests of ridges and mountain peaks.
Field identification & locations
Identify by its hardness (scratches glass) and sand-like sugary texture. Unlike sandstone, quartzite fractures through the grains rather than around them. Found globally in metamorphic terrains.
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