metamorphic
Quartzite
Quartzite (chiefly SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or yellow/brown (iron-stained); Luster: vitreous or dull; Structure: non-foliated granoblastic; Fracture: conchoidal or irregular
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or yellow/brown (iron-stained)
- Luster
- vitreous or dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or yellow/brown (iron-stained); Luster: vitreous or dull; Structure: non-foliated granoblastic; Fracture: conchoidal or irregular
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause quartz grains to recrystallize and fuse into a dense, crystalline mass. These rocks can date back to any geological era from the Precambrian to more recent times.
Uses & applications
Used as crushed stone for road construction, railway ballast, and in the manufacturing of glass and ceramics. Polished varieties are used for kitchen countertops and decorative flooring.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks in a landscape, forming prominent ridges and hills. It is harder and more durable than the parent sandstone from which it originated.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass) and the fact that it breaks through the quartz grains rather than around them. Commonly found in mountain ranges and areas with ancient metamorphic basement rock.
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