metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 on Mohs scale. Color: Light greyish-white with faint banding. Luster: Dull to vitreous, smooth water-worn surface texture. Crystal structure: Microcrystalline, interlocking quartz grains. Cleavage: None (conchoidal/irregular fracture).
- Hardness
- 7 on Mohs scale
- Color
- Light greyish-white with faint banding
- Luster
- Dull to vitreous, smooth water-worn surface texture
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Physical properties
Hardness: 7 on Mohs scale. Color: Light greyish-white with faint banding. Luster: Dull to vitreous, smooth water-worn surface texture. Crystal structure: Microcrystalline, interlocking quartz grains. Cleavage: None (conchoidal/irregular fracture).
Formation & geological history
Formed through the regional or contact metamorphism of quartz sandstone under intense heat and pressure, causing quartz grains to recrystallize into an interlocking mosaic. Later eroded and rounded by stream or beach action into a smooth pebble.
Uses & applications
Used in construction as crushed stone, road ballast, decorative garden pebbles, and historical use for stone tools due to high hardness.
Geological facts
Quartzite is so durable that it often survives multiple cycles of erosion, weathering, and deposition. Unlike sandstone, quartzite fractures through quartz grains rather than along grain boundaries.
Field identification & locations
Identify in the field by its extreme hardness (scratches glass easily, cannot be scratched by steel), smooth rounded river/beach cobble morphology, and interlocking granular texture. Commonly found in riverbeds, glacial deposits, and coastal beaches.
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