metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Ranges from white and gray to pink, brown, or reddish due to iron oxide impurities; Luster: Vitreous to greasy; Crystal structure: Trigonal (microcrystalline quartz grains fused together); Cleavage: None (fractures conchoidally); Specific gravity: 2.65.
- Hardness
- 7 on Mohs scale
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 7 on Mohs scale; Color: Ranges from white and gray to pink, brown, or reddish due to iron oxide impurities; Luster: Vitreous to greasy; Crystal structure: Trigonal (microcrystalline quartz grains fused together); Cleavage: None (fractures conchoidally); Specific gravity: 2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or chert under high temperatures and pressures, typically in mountain-building belts. Can date back billions of years depending on the parent rock formation.
Uses & applications
Used in construction as crushed stone, railroad ballast, dimension stone, manufacturing of silica brick, and sometimes as a decorative stone or in countertops.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why ridges formed of quartzite often survive as prominent hills or mountain crests.
Field identification & locations
Identified by its high hardness (scratches glass easily), lack of reaction to acid, and sugary textured surface where broken. Found globally in ancient orogenic belts.
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