metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale. Color ranges from white and gray to pink, red, or purple due to iron oxide impurities. Luster is vitreous to greasy on fresh surfaces. Crystal structure is interlocking quartz grains (non-foliated). Conchoidal fracture. Specific gravity is approximately 2.65.
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Physical properties
Hardness of 7 on the Mohs scale. Color ranges from white and gray to pink, red, or purple due to iron oxide impurities. Luster is vitreous to greasy on fresh surfaces. Crystal structure is interlocking quartz grains (non-foliated). Conchoidal fracture. Specific gravity is approximately 2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or chert under high temperature and tectonic pressure. The original quartz grains recrystallize and weld tightly together. Geological age varies widely from Precambrian to Cenozoic.
Uses & applications
Used in construction, road aggregate, railway ballast, manufacturing of silica brick, and sometimes as a decorative stone or countertop material due to its durability.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why mountains made of quartzite often form the highest ridges and peaks in many mountain ranges.
Field identification & locations
Can be identified in the field by its hardness (scratches glass easily), the way it breaks across rather than around quartz grains (unlike sandstone), and its sugary texture on broken surfaces. Found worldwide.
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