metamorphic
Quartzite pebble
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-white with yellow-brown iron staining; Luster: Waxy to vitreous; Structure: Granular, crystalline; Cleavage: None (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- Grayish-white with yellow-brown iron staining
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-white with yellow-brown iron staining; Luster: Waxy to vitreous; Structure: Granular, crystalline; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, usually during mountain-building events. This specific specimen has been further shaped and smoothed by water erosion in a river or beach environment.
Uses & applications
Used in construction as crushed stone, in railway ballast, and occasionally as a decorative landscape stone or in industrial glass making.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, remaining as pebbles and boulders long after softer rocks have worn away. The yellowish tint is likely due to limonite or iron oxide staining.
Field identification & locations
Identify by its ability to scratch glass and its grainy, sandpaper-like sparkle despite being smooth to the touch. These are extremely common in glacial deposits and riverbeds globally.
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