metamorphic
Quartzite
Quartzite (chiefly SiO2)
Hardness: 7 on Mohs scale; Color: typically pink/red due to iron oxide impurities; Luster: vitreous to dull; Crystal structure: granular, non-foliated; Cleavage: none; Specific gravity: approx. 2.65.
- Hardness
- 7 on Mohs scale
- Color
- typically pink/red due to iron oxide impurities
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically pink/red due to iron oxide impurities; Luster: vitreous to dull; Crystal structure: granular, non-foliated; Cleavage: none; Specific gravity: approx. 2.65.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, causing quartz grains to recrystallize and fuse together. Often Proterozoic or Paleozoic in age.
Uses & applications
Used in construction as crushed stone or ballast, dimension stone for flooring and walls, and in lapidary work for tumbled stones or decorative carvings.
Geological facts
Quartzite is so hard that it can scratch steel and glass. In some cases, the original bedding of the parent sandstone is preserved even through the metamorphic process, resulting in the bands seen here.
Field identification & locations
Identify by its extreme hardness and granular texture; it will break across the grains rather than around them. Commonly found in glaciated regions (as pebbles/cobbles) or in mountain belts like the Appalachians or Alps.
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