metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale; color ranges from white and gray to pink, yellow, or brown due to iron oxide impurities; vitreous to greasy luster; non-foliated crystal structure; lacks cleavage and fractures conchoidally; specific gravity around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale; color ranges from white and gray to pink, yellow, or brown due to iron oxide impurities; vitreous to greasy luster; non-foliated crystal structure; lacks cleavage and fractures conchoidally; specific gravity around 2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or chert under intense heat and tectonic pressure, typically in mountain-building events over millions of years.
Uses & applications
Used in construction, as crushed stone for roadbeds, railway ballast, dimension stone, in the manufacture of glass, and occasionally as an ornamental stone or in countertops.
Geological facts
Because quartz is extremely resistant to weathering, quartzite ridges often form prominent, high resistance mountain ranges and ridges compared to surrounding softer rock.
Field identification & locations
Can be identified in the field by its sugary texture, inability to be scratched by a knife or glass, and the fact that it breaks across the quartz grains rather than around them, unlike sandstone.
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