metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale; colors range from white and gray to green, blue, pink, or yellow due to impurities; vitreous to greasy luster; non-foliated, granular crystal structure; conchoidal fracture with no distinct cleavage; specific gravity around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale; colors range from white and gray to green, blue, pink, or yellow due to impurities; vitreous to greasy luster; non-foliated, granular crystal structure; conchoidal fracture with no distinct cleavage; specific gravity around 2.65.
Formation & geological history
Formed from quartz-rich sandstone or chert under high temperature and pressure during regional or contact metamorphism, typically dating from various geological eras spanning millions of years.
Uses & applications
Used widely in construction, as crushed stone for roadbeds, in manufacturing railroad ballast, for decorative facing stone, and in some specialized industrial applications like refractory bricks.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why ridges formed of quartzite often remain as prominent hills or mountain crests while surrounding rocks erode away.
Field identification & locations
Can be identified in the field by its hardness (scratches glass easily), lack of foliation, and sugary textured fractured surfaces where individual quartz crystals interlock tightly. Common globally.
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