metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Tan to reddish-brown (caused by iron oxide staining); Luster: Sub-vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan to reddish-brown (caused by iron oxide staining)
- Luster
- Sub-vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan to reddish-brown (caused by iron oxide staining); Luster: Sub-vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure caused quartz grains to recrystallize and fuse together. This specimen shows signs of water-worn erosion, likely from a riverbed or glacial deposit.
Uses & applications
Commonly used as high-quality construction aggregate, railway ballast, and in decorative landscaping or rock tumbling.
Geological facts
Quartzite is so tough that it often survives intense mechanical weathering that breaks down other rocks. It is harder than steel and will easily scratch a glass plate.
Field identification & locations
Identify in the field by its hardness (will scratch glass) and its grainy, sugary texture. Unlike sandstone, quartzite breaks through the quartz grains rather than around them. Common in mountainous regions and glacial drift.
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