metamorphic
Red Quartzite
Quartzite (principally SiO2)
Hardness: 7 on Mohs scale; Color: Reddish-brown to pink due to iron oxide impurities; Luster: Vitreous to dull; Structure: Granoblastic (interlocking quartz grains); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Reddish-brown to pink due to iron oxide impurities
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Reddish-brown to pink due to iron oxide impurities; Luster: Vitreous to dull; Structure: Granoblastic (interlocking quartz grains); Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone subjected to high heat and pressure, typically during mountain-building events. The original sand grains are recrystallized into an interlocking mosaic of quartz.
Uses & applications
Used in construction as road ballast, gravel, and dimension stone. High-quality specimens are sometimes used as decorative stones or in landscaping.
Geological facts
Quartzite is so tough that it often survives intense erosion better than the surrounding rocks, frequently forming the tops of ridges and mountain peaks. It is harder than a steel knife and will scratch glass easily.
Field identification & locations
Identify in the field by its hardness (cannot be scratched by a knife) and its grainy, sugary texture. It breaks across grains rather than around them. Found commonly in ancient mountain belts and shield areas like the Appalachians or the Canadian Shield.
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