metamorphic
Quartzite pebble
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Greyish-white with pink/orange iron staining; Luster: Vitreous to dull; Crystal structure: Non-foliated, interlocking quartz crystals; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Greyish-white with pink/orange iron staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Greyish-white with pink/orange iron staining; Luster: Vitreous to dull; Crystal structure: Non-foliated, interlocking quartz crystals; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events (orogeny). This specific specimen shows signs of fluvial or coastal erosion, giving it a rounded 'pebble' shape.
Uses & applications
Used as a high-quality railway ballast, in construction as crushed stone, for glass manufacturing (if high purity), and in landscaping. Polished pebbles are often used in decorative gardening and aquariums.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, ending up as rounded pebbles in riverbeds or on beaches thousands of miles from its original formation site.
Field identification & locations
Identify in the field by its inability to be scratched by steel and its grainy, 'sugary' texture on fresh breaks. Found globally in ancient mountain belts. To collect, look for rounded, translucent to opaque stones in stream beds or gravel pits.
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