metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: tan, yellow, or light brown due to iron oxide impurities; Luster: vitreous to dull; Crystal structure: trigonal (microcrystalline); Cleavage: none, breaks with conchoidal fracture.
- Hardness
- 7 on Mohs scale
- Color
- tan, yellow, or light brown due to iron oxide impurities
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: tan, yellow, or light brown due to iron oxide impurities; Luster: vitreous to dull; Crystal structure: trigonal (microcrystalline); Cleavage: none, breaks with conchoidal fracture.
Formation & geological history
Formed from the metamorphism of quartz sandstone under high heat and pressure, typically during mountain-building events. This process causes the quartz grains to recrystallize and fuse together.
Uses & applications
Used in construction for road ballast, floor tiles, and vanity tops. It is also used as decorative stone and in the glass-making industry when purity is high.
Geological facts
Quartzite is so durable that it can withstand intense weathering; it often forms the crests of ridges and resistant hilltops. It is much harder than the sandstone it originates from.
Field identification & locations
Identify in the field by its hardness (it will scratch glass) and lack of reaction to acid. It is commonly found in riverbeds as rounded pebbles. Found globally in ancient mountain belts and shield areas.
