metamorphic
Quartzite (Iron-stained)
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Pinkish-orange toward tan due to iron oxide staining; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- Pinkish-orange toward tan due to iron oxide staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Pinkish-orange toward tan due to iron oxide staining; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.
Formation & geological history
Quartzite forms through the metamorphism of quartz-rich sandstone under intense heat and pressure. This specific rounded specimen is a river-worn pebble, indicating it was transported and tumbled by water over a long geological period.
Uses & applications
Used as decorative garden stone, in construction as aggregate, and occasionally for primitive stone tools due to its hardness and durability.
Geological facts
Quartzite is so tough that it often resists weathering better than other rocks, frequently capping hills and mountain ridges. The orange-red color is not inherent to the quartz but is a result of hematite or limonite impurities.
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife and its tendency to break across quartz grains rather than around them. Commonly found in riverbeds and glacial deposits.
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