metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: light gray to tan with granular texture, Luster: vitreous to dull, Crystal structure: trigonal (recrystallized quartz grains), Cleavage: poor/conchoidal fracture
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Physical properties
Hardness: 7 (Mohs scale), Color: light gray to tan with granular texture, Luster: vitreous to dull, Crystal structure: trigonal (recrystallized quartz grains), Cleavage: poor/conchoidal fracture
Formation & geological history
Originates from the metamorphism of quartz sandstone under high heat and pressure, typically during tectonic plate collisions and mountain-building events.
Uses & applications
Used extensively in road construction (railway ballast), glass manufacturing, and as decorative stone for counter tops or landscaping.
Geological facts
Quartzite is so durable that it can withstand intense weathering; it often forms the crests of mountain ranges and resistant ridges. It is harder and tougher than its parent rock, sandstone.
Field identification & locations
Identify in the field by its grainy, 'sugar-like' appearance and the fact that it scratches glass and steel. It is commonly found in ancient mountain belts and river beds.
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