metamorphic
Quartzite Pebble (with iron staining)
Quartzite (SiO2 with ferric oxide impurities)
Hardness: 7 on Mohs scale; Color: Yellowish-orange to off-white; Luster: Vitreous to waxy; Structure: Granoblastic, non-foliated; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Yellowish-orange to off-white
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Yellowish-orange to off-white; Luster: Vitreous to waxy; Structure: Granoblastic, non-foliated; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz sandstone under high heat and pressure. The sandy grains recrystallize into a dense interlocking map of quartz crystals. This specimen shows water-worn rounding, likely from a riverbed or coastal environment.
Uses & applications
Used in construction as crushed stone or road ballast, as a refractory material in glassmaking, and frequently as decorative landscaping stones or garden 'river rocks'.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, ending up as rounded pebbles in stream beds millions of years after its formation. The yellow hue is caused by secondary iron oxide (limonite) staining.
Field identification & locations
Identify by its ability to scratch glass and its grainy, 'sugary' texture under magnification. Commonly found in mountain ranges or ancient glacial till. It will not react with acid, unlike similar-looking marble.
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