metamorphic
Quartzite
Quartzite
Hardness: 7 on Mohs scale; Color: typically white to gray, often pink or reddish due to iron oxide; Luster: vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: none; Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, often pink or reddish due to iron oxide; Luster: vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: none; Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. Under intense heat and pressure, quartz grains recrystallize and fuse together. Often found in Precambrian and Paleozoic mountain belts.
Uses & applications
Used in construction as crushed stone for road beds or railroad ballast, as dimension stone for wall coverings and flooring, and occasionally in glassmaking if pure enough.
Geological facts
Quartzite is so tough that it often survives intense weathering that breaks down other rocks, frequently forming the resistant caps of ridges and mountains. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify in the field by its extreme hardness and grainy, sugary texture that resembles sandstone but will not rub off grains. It breaks across grains rather than around them. Found globally in metamorphic terrains like the Appalachians or Alps.
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