metamorphic
Red Quartzite
Quartzite (SiO2 with iron oxide inclusions)
Hardness: 7 on Mohs scale; Color: Reddish-brown to pink due to hematite; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Reddish-brown to pink due to hematite
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Reddish-brown to pink due to hematite; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause quartz grains to recrystallize and fuse together. Often associated with ancient mountain-building events (Orogeny).
Uses & applications
Used as decorative stone in landscaping, crushed stone for road construction and railway ballast, and occasionally for lapidary work like cabochons or tumbled stones.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, frequently forming the tops of ridges and resistant hills.
Field identification & locations
Identify in the field by its extreme hardness (it will scratch glass and steel) and its grainy, sugary texture that looks like sandstone but cannot be scratched off. Common in the Appalachian Mountains and Lake Superior region.
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