metamorphic
Quartzite
Quartzite (composed primarily of SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or pink/reddish due to iron oxides; Luster: vitreous to dull; Structure: non-foliated, granular; Cleavage: none (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or pink/reddish due to iron oxides
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or pink/reddish due to iron oxides; Luster: vitreous to dull; Structure: non-foliated, granular; Cleavage: none (conchoidal fracture).
Formation & geological history
Formed through the regional metamorphism of quartz starch sandstone. Under high heat and pressure, quartz grains recrystallize and fuse together, creating a dense, hard rock. Typically Precambrian to Paleozoic in age.
Uses & applications
Used as crushed stone for road construction, railway ballast, building stone, floor tiles, and as a source of silica for glass manufacturing. High-quality specimens are used for countertops and ornamental carvings.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock, forming resistant ridges and hilltops. Unlike sandstone, which breaks between grains, quartzite breaks through the quartz grains themselves.
Field identification & locations
Identify by its hardness (it will easily scratch glass) and its sparkling, sugary appearance on fresh surfaces. Often found in mountain ranges and areas with ancient continental crust exposed.
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