metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Reddish-brown due to iron oxide; Luster: Dull to vitreous; Crystal structure: Granoblastic/Non-foliated; Cleavage: None; Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- Reddish-brown due to iron oxide
- Luster
- Dull to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Reddish-brown due to iron oxide; Luster: Dull to vitreous; Crystal structure: Granoblastic/Non-foliated; Cleavage: None; Specific gravity: 2.6-2.7.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, typically in orogenic (mountain-building) belts. This specific specimen appears to be a water-worn river pebble.
Uses & applications
Used as crushed stone for road construction, railway ballast, and occasionally as a decorative stone or lapidary material if highly colored.
Geological facts
Quartzite is so durable that it often outlasts the mountains it was formed in, remaining as resistant pebbles in riverbeds or on beaches long after softer rocks have eroded away.
Field identification & locations
Identify in the field by its extreme hardness (it will scratch glass easily) and its sugary, crystalline texture. It is commonly found in glacial till, riverbeds, and mountain ranges worldwide.
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