metamorphic
Quartzite river pebble
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Tan to yellowish-brown; Luster: Dull to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan to yellowish-brown
- Luster
- Dull to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan to yellowish-brown; Luster: Dull to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure. This specific specimen has been further shaped by fluvial (river) erosion, which rounded its edges over time.
Uses & applications
Used frequently in construction as road ballast, in glass manufacturing if pure, and as decorative river stones for landscaping.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks and persists as rounded boulders or pebbles long after softer rocks have eroded away. It is significantly harder than the sandstone from which it is derived.
Field identification & locations
Identify in the field by its hardness (will scratch glass) and lack of distinct grains compared to sandstone. Commonly found in riverbeds, glacial deposits, and mountain ranges.
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