metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, often with tan or pinkish tints; Luster: vitreous to dull; Structure: non-foliated, granular; Cleavage: none (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- typically white to gray, often with tan or pinkish tints
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, often with tan or pinkish tints; Luster: vitreous to dull; Structure: non-foliated, granular; Cleavage: none (conchoidal fracture).
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events (orogeny).
Uses & applications
Used as crushed stone for road construction, railroad ballast, and building materials; also used for decorative interior stone (countertops) and as a source of silica in glass manufacturing.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks, forming the caps of ridges and mountain peaks. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify by its extreme hardness and grainy, sugary texture that looks like sand but does not rub off. Common in glaciated areas as river pebbles or in metamorphic mountain belts like the Appalachians or Alps.
