metamorphic
Red Quartzite (River Pebble)
Quartzite (primarily Silicon Dioxide - SiO2)
Hardness: 7 on the Mohs scale. Color: Reddish-tan to pink due to iron oxide impurities. Luster: Vitreous to dull. Crystal structure: Hexagonal (microcrystalline/granular). Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.7.
- Hardness
- 7 on the Mohs scale
- Color
- Reddish-tan to pink due to iron oxide impurities
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on the Mohs scale. Color: Reddish-tan to pink due to iron oxide impurities. Luster: Vitreous to dull. Crystal structure: Hexagonal (microcrystalline/granular). 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. This specific specimen has been rounded and polished by fluvial (river) or glacial transport over thousands to millions of years.
Uses & applications
Used primarily in construction as crushed stone or road ballast. High-purity quartzite is used in the glass and ceramic industries. Polished pebbles are a common staple in landscaping, aquariums, and decorative garden paths.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock, forming resistant ridges or mountain peaks. Its color is a reliable indicator of mineral impurities; while pure quartzite is white, the presence of hematite often turns it shades of red and pink.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass or steel) and its granular, sugary texture on a fresh break. Commonly found in riverbeds, glacial tills, and ancient mountain belts across North America (e.g., the Baraboo Quartzite) and Europe.
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